Lawn care robot

ABSTRACT

A robot lawnmower includes a body and a drive system carried by the body and configured to maneuver the robot across a lawn. The robot also includes a grass cutter and a swath edge detector, both carried by the body. The swath edge detector is configured to detect a swath edge between cut and uncut grass while the drive system maneuvers the robot across the lawn while following a detected swath edge. The swath edge detector includes a calibrator that monitors uncut grass for calibration of the swath edge detector. In some examples, the calibrator comprises a second swath edge detector.

CROSS REFERENCE TO RELATED APPLICATIONS

This U.S. patent application is a continuation of, and claims priorityunder 35 U.S.C. §120 from, U.S. application Ser. No. 11/688,225, filedon Mar. 19, 2007, and entitled “LAWN CARE ROBOT,” which claims priorityunder 35 U.S.C. 119(e) from U.S. provisional patent application60/783,268, filed Mar. 17, 2006, and entitled “LAWN CARE ROBOT,” fromU.S. provisional patent application 60/803,030, filed May 23, 2006, andentitled “LAWNMOWER HAVING RECIPROCATING SHEARS,” and from U.S.provisional patent application 60/865,069, filed Nov. 9, 2006, andentitled “HIGHLY MANEUVERABLE AUTONOMOUS PLATFORM.” The entire contentsof U.S. application Ser. No. 11/688,225 and all three priorityprovisional applications are hereby incorporated by reference.

TECHNICAL FIELD

The disclosure relates to an autonomous robot that can perform lawn caretasks.

BACKGROUND

Autonomous robots that perform household functions such as floorcleaning and lawn cutting are now readily available consumer products.Commercially successful robots are not unnecessarily complex, andgenerally operate randomly within a confined area. In the case of floorcleaning, such robots are generally confined within (i) touched wallsand other obstacles within the rooms of a dwelling, (ii) IR-detectedstaircases (cliffs) down; and/or (iii) user placed detectable barrierssuch as directed IR beams, physical barriers or magnetic tape. Wallsprovide most of the confinement perimeter. Other, much less ubiquitousrobots may try to localize or to map the dwelling using a complex systemof sensors and/or active or passive beacons (e.g., sonar, RFID or barcode detection, or various kinds of machine vision).

There are examples of consumer robotic lawn mowers that use a similar“invisible” barrier—a continuous guide conductor boundary proposed forconfining random motion robotic mowers by the early 1960's (See, e.g.,U.S. Pat. Nos. 3,128,840; 3,550,714). Examples include commercialproducts by Electrolux, Husqvarna, Zucchetti S. A., Belrobotics, andFriendly Robotics. The guide conductor is intended to confine the robotwithin the lawn or other appropriate area, so as to avoid damagingnon-grassy areas of the yard or intruding onto a neighboring property.The conductor is one continuous loop around the property to be mowed.Although the guide conductor can be drawn into the property inpeninsulas to surround gardens or other off-limits areas, it remains acontinuous loop, and is energized with an AC current detectable as amagnetic field at a few feet. The guide conductor must be supplied withpower, usually from a wall socket. Within the bounded area, the knownrobots may “bounce” randomly as the robot nears the guide conductor, ormay follow along the guide conductor. Some of the mowers also touch andbounce from physical barriers. More complex commercial mowers may try tolocalize or to map the mowing area, again using a complex system ofsensors and/or active or passive beacons (e.g., sonar, encoded opticalretro-reflector detection, machine vision).

SUMMARY

In one aspect, a robot lawnmower includes a body and a drive systemcarried by the body and configured to maneuver the robot across a lawn.The robot also includes a grass cutter and a swath edge detector, bothcarried by the body. The swath edge detector is configured to detect aswath edge between cut and uncut grass while the drive system maneuversthe robot across the lawn while following a detected swath edge. Theswath edge detector includes a calibrator that monitors uncut grass forcalibration of the swath edge detector. In some examples, the calibratorcomprises a second swath edge detector.

Implementations of this aspect of the disclosure may include one or moreof the following features. In some implementations, the swath edgedetector includes an array of grass length sensors spanning a distancecomprising at least a steering error distance and a grass length sensorwidth. In one example, the swath edge detector has a width of betweenabout 4 and about 10 inches. A first portion of the array is arranged todetect the swath edge and a second portion of the array is arranged tomonitor uncut grass.

In some implementations, the swath edge detector includes a plurality ofsensor components. Each sensor component includes a sensor housingdefining a cavity and a cavity opening configured to allow grass entrywhile inhibiting direct sunlight into the cavity. Each sensor componentalso includes an emitter carried by the housing in the cavity andconfigured to emit an emission across the cavity opening. A receiver,carried by the housing, is configured to receive a grass-reflectedemission and is positioned in the cavity to avoid exposure to directsunlight. The emission may be infrared light. In some examples, thecalibrator includes at least one of the sensor components.

In another implementation, the swath edge detector includes multipleprojections extending downwardly from the body and an emissive sensormounted to each projection. The emissive sensor has an emitter and areceiver. The emitter is configured to emit an emission and the receiveris configured to detect the emission as reflected. In some examples, thecalibrator includes at least one of the projections.

In yet another implementation, the swath edge detector includes firstand second electrically conductive projections extending downwardly fromthe body. The second projection is longer than the first projection. Thefirst and second projections are configured to form an electric circuitwith moist grass contacting the first and second projections.

In some implementations, the swath edge detector includes first andsecond projections extending downwardly from the body. The firstprojection is longer than the second projection and a vibration sensoris secured to each projection and is responsive to vibrations therein.The projections may be crenulated flaps.

The robot lawnmower includes a grass orientor, in some examples, carriedby the body forward of the swath edge detector and configured to orientgrass. The grass orientor may be a flattening wheel.

In some instances, the robot lawnmower includes a not-lawn detectorcarried by the body and responsive to non-grass surfaces, wherein thedrive system is configured to redirect the robot in response to thedetector detecting a non-grass surface. The not-lawn detector includes asensor housing defining emitter and receiver receptacles. An audiotransmitter is carried in the emitter receptacle and transmits an audioemission. A receiver is carried in the receiver receptacle and isconfigured to receive an audio emission reflected off a ground surface.A controller of the robot compares a received reflected audio emissionwith a threshold energy to detect a non-grass surface. The audiotransmitter transmits multiple audio emissions starting at a fundamentalfrequency and successively increasing the wavelength of each emission byhalf the fundamental frequency. For example, the audio transmittertransmits a first audio emission at about 6.5 kHz and a second audioemission at about 8.67 kHz. The controller receives the reflected audioemission from the receiver though a narrow band-pass amplifier. Ananti-vibration mounting system secures the receiver in the receiverreceptacle. The anti-vibration mounting system includes a first elasticsupport holding the receiver in a tube below a sound absorber. The tubeis secured in the receiver receptacle with a second elastic supporthaving a lower durometer than the first elastic support.

In some examples, the not-lawn detector includes four different colorednarrow-spectrum light emitters and an optical receiver that receivesreflected light from the emitters. The optical receiver is configured todetect grass by evaluating the received light. In other examples, thenot-lawn detector is responsive to a pH of the lawn.

The robot lawnmower may include a side trimmer carried on a periphery ofthe body and configured to cut lawn adjacent the body. The body maydefine a substantially circular profile in a horizontal plane or asubstantially pentagonal profile in a horizontal plane.

The robot lawnmower may include at least one grass erector carried bythe body and configured to erect grass. The grass erector includes adriven wheel having an axis of rotation parallel to the lawn and aplurality of flexible grass agitators extending radially outward fromthe wheel. The robot lawnmower may also include a stasis detectorcarried by the body.

In another aspect, a robot lawnmower swath edge detector system includesa controller carried by a body of a robot and a plurality of grasslength sensors carried by the body and in communication with thecontroller. Each grass length sensors includes a sensor housing defininga cavity and a cavity opening configured to allow grass entry whileinhibiting direct sunlight into the cavity. An emitter is carried by thehousing in the cavity and is configured to emit an emission across thecavity opening. A receiver is carried by the housing and is configuredto receive a grass-reflected emission. The receiver is positioned in thecavity to avoid exposure to direct sunlight. The controller comparesoutputs from multiple ones of the grass length sensors to determine aswath edge location. In some implementations, the plurality of grasslength sensors spans a distance comprising at least a steering errordistance and a grass length sensor width. In one example, the pluralityof grass length sensors spans a distance of between about 4 and about 10inches.

In yet another aspect, a robot lawnmower includes a first body portiondefining a payload area and carrying a drive system having at least onedriven wheel. The driven wheel has a diameter sized to circumscribe thepayload area. A controller is figured to control the drive system tomaneuver the lawnmower to traverse a lawn while cutting grass. A secondbody portion is joined to the first body portion by an articulated jointand carries at least one free wheel. An actuator is actuable to rotatethe first body portion relative to the second body portion at thearticulated joint in response to a signal received from the controller.A grass cutter is carried by at least one of the first and second bodyportions.

Implementations of this aspect of the disclosure may include one or moreof the following features. In some implementations, the driven wheel issupported by multiple rollers carried by the first body portion anddriven by a pinion coupled to a motor carried by the first body portion.The free wheel pivots along an axis perpendicular to an axis ofrotation.

In some examples, the robot lawnmower includes a swath edge detectorcarried by the first body portion and configured to detect a swath edgebetween cut and uncut grass. The drive system is configured to maneuverthe robot across the lawn while following a detected swath edge. Theswath edge detector includes a calibrator carried by the body andconfigured to monitor uncut grass. The controller is in communicationwith the calibrator and is configured to periodically compare thedetected swath edge with monitored uncut grass.

In another aspect, a method of lawn cutting with a robot includesdetecting a swath edge with a swath edge detector carried by the robotas the robot maneuvers itself across a lawn and automatically comparinga detected swath edge with uncut grass monitored by a calibrator carriedby the robot. The method includes following the detected swath edge anderecting blades of grass of the lawn with a grass erector of the robot.The method includes cutting the lawn with a cutter of the robot andarranging blades of grass of the lawn with a grass arranger carried bythe robot.

Implementations of this aspect of the disclosure may include one or moreof the following features. In some implementations, the method includesorienting blades of grass of the lawn with a grass orientor carried bythe robot. The method may also include continuously scanning for anabsence of lawn with a not-lawn detector carried by the robot, andautomatically redirecting the robot in response to detecting an absenceof lawn. Another method step may include scanning for a body of liquidproximate the robot with a liquid detector carried by the robot, andautomatically redirecting the robot in response to detecting a body ofliquid. In some implementations, the method includes scanning for apotential obstacle proximate the robot with a proximity sensor carriedby the robot, and automatically redirecting the robot in response todetecting a potential obstacle. The method may also include scanning fora boundary responder with a boundary detector carried by the robot, andautomatically redirecting the robot in response to detecting a boundaryresponder.

The details of one or more implementations of the disclosure are setfourth in the accompanying drawings and the description below. Otherfeatures, objects, and advantages will be apparent from the descriptionand drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of lawn care robots.

FIG. 1B is a schematic view of a method of lawn cutting with a roboticlawnmower.

FIGS. 2A-2C are schematic views of lawn care robots.

FIGS. 3A-3K are schematic and block diagram views of lawn care robots.

FIG. 4A is a side view of a lawn care robot.

FIG. 4B is a rear view of a lawn care robot.

FIG. 4C-D are top views of a lawn care robot.

FIG. 4E is a side view of a lawn care robot.

FIG. 4F is a rear view of a lawn care robot.

FIG. 4G is a top view of a lawn care robot.

FIG. 4H is a side view of a lawn care robot.

FIG. 4I is a top view of a lawn care robot.

FIG. 4J is a side view of a drive wheel of a lawn care robot.

FIG. 4K-N are front views of a drive wheel of a lawn care robot.

FIG. 5A is a schematic view of a rotary cutter.

FIG. 5B is an exploded view of a rotary cutter.

FIGS. 5C-D are schematic views of a reciprocating cutter.

FIG. 5E is a schematic view of a comb of a reciprocating cutter.

FIGS. 5F-G are schematic views of a reciprocating cutter.

FIGS. 5H-I are schematic views of cutters.

FIG. 6A is a schematic view of a hybrid mechanical-electric roboticmower system.

FIG. 6B is a schematic view of an all electric robotic mower system.

FIG. 6C is a schematic view of a robotic mower system.

FIG. 6D is a table of components for a robotic mower system.

FIG. 6E is a schematic view of grass-cutting obstacles, boundaries, andcuttable areas in a neighborhood.

FIGS. 7A-B are schematic views of methods of navigating a mower.

FIG. 7C is a schematic view of a robotic mower and a handle.

FIG. 7D is a schematic view of a robotic mower with a handle.

FIG. 7E is a schematic view of a robotic mower with a stowed handle.

FIG. 7F is a schematic view of a robotic mower with a handle.

FIG. 8A is a schematic view of an optical not-grass detector.

FIG. 8B is a diagram illustrating an example response of an opticalnot-grass detector over time.

FIGS. 8C-D are schematic views of acoustic not-grass detectors.

FIG. 8E is a schematic view of an acoustic hard surface detector.

FIG. 8F is a diagram of a process of classifying a target surface withan acoustic hard surface detector.

FIG. 8G is a schematic view of a mounting system for an emitter orreceiver of an acoustic hard surface detector.

FIG. 9 is a schematic view of a liquid detector.

FIG. 10 is a schematic view of a cut edge detector.

FIGS. 11A-B are schematic views of cut edge detectors.

FIG. 12 is a rear schematic view of a lawn care robot having a cut edgedetector and a calibrator.

FIG. 13 is a schematic view of a cut edge detector.

FIG. 14 is a schematic view of an optical sensor.

FIG. 15A is a schematic view of a cut edge detector.

FIG. 15B is a top schematic view of a lawn care robot.

FIG. 16A-B are schematic views of cut edge detectors.

FIG. 16C is a schematic view of a grass height row vector.

FIG. 16D is a schematic view of a two-dimensional grass height rowvector array.

FIG. 16E is a schematic view of a grass height image from a cut edgedetector.

FIGS. 17-19 are schematic views of cut edge detectors.

FIG. 20 is a rear schematic view of a lawn care robot having a cut edgedetector and a calibrator.

FIGS. 21-22 are schematic views of cut edge detectors.

FIG. 23A is a schematic view of a lawn care robot system and mowingrobot encountering a boundary responder.

FIG. 23B is a schematic view of boundary responder detector for a lawncare robot system.

FIGS. 24-29 are schematic views of boundary responders.

FIG. 30 is a schematic view of a property having boundaries, obstacles,cuttable areas, and non-cuttable areas.

FIG. 31 is a schematic view of a property having boundary responders.

FIG. 32 is a schematic view of a property having follow and enterresponders.

FIG. 33 is a schematic view of a lawn care robot.

FIG. 34 is a schematic view of an example cutting pattern mowed by alawn care robot.

FIG. 35A is a schematic view of a property with a perimeter boundaryhaving splice connectors, power stations, and an anchor.

FIG. 35B is a schematic view of a splice connector.

FIG. 35C is a schematic view of a robot-activated power station.

FIG. 35D is a schematic view of a perimeter boundary having spliceconnectors and power stations.

FIG. 36 is a schematic view of a property with a perimeter boundaryhaving splice connectors, power stations, and boundary responders.

FIG. 37 is a schematic view of a spike type boundary responder.

FIG. 38 is a schematic view of a spike type boundary responderinstallation tool.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

An autonomous robot may be designed to clean flooring. For example, theautonomous robot may vacuum carpeted or hard-surfaces and wash floorsvia liquid-assisted washing and/or wiping and/or or electrostatic wipingof tile, vinyl or other such surfaces. U.S. Pat. No. 6,883,201 by Joneset al. entitled AUTONOMOUS FLOOR CLEANING ROBOT, the disclosure of whichis herein incorporated by reference it its entirety, discloses anautonomous cleaning robot. Notwithstanding the use of the term mowingrobot herein, these concepts may also apply to a cleaning or othercoverage robot.

Referring to FIGS. 1-3, an autonomous coverage robot 10 includes a body100, a surface treater 200 secured to the body 100, and at least onesurface sensor 310, 320, 330 carried by the body 100 and responsive toat least one surface characteristic. A drive system 400 is carried bythe body 100 and configured to maneuver the robot 10 across a surface 20while following at least one surface characteristic. Examples of thesurface treater 200 include a reciprocating symmetrical cutter floatingon a following wheel 210, a rotary cutter, a spreader, and a gatherer.The body 100, as shown in FIG. 1A, has a substantially circularperimeter; however, other shapes are suitable as well, such as asubstantially pentagonal, tombstone, or rectangular shape, as shown inFIGS. 2A-3. In some implementations, the robot 10 comprises aframe-and-body structure or a substantially monocoque structure. In someimplementations, the body 100 includes a two part articulated body,which will be described later in detail.

In some examples, one or more edge following sensors 310 (also referredto as cut edge detectors) and edge calibrators 320 (e.g. a grasscharacter sensor) are mounted on the body 100. FIG. 1A depicts anexemplary placement of boundary sensors 340, a bumper 110 (which may becoupled to two or more displacement sensors to provide impactdirectionality) and at least one grass sensor 330 (e.g. determines apresence of grass) on the body 100. An active or passive fore grasscomber 510 precedes the surface treater 200 and an aft grass comber 520follows each wheel 410, 420, 430.

Referring to FIG. 1B, a method of lawn cutting with a robotic lawnmower10 having a drive system 400 and a cutter 200 carried by a body 100includes step S10 of activating the drive system 400 to maneuver therobotic lawnmower 10 across a lawn 20, step S30 of detecting a swathedge 26 with the swath edge detector 310, and step S40 of following adetected swath edge. The method may include step S20 of orienting bladesof grass of the lawn 20 with a grass arranger 440 carried by the body100 forward of a swath edge detector 310 carried by the body 100. Themethod includes step S50 of erecting blades of grass of the lawn 20 witha fore grass comber 510 carried by the body forward 100 of the cutter200, step S60 of cutting the lawn 20 with the cutter 200, and step S70of arranging blades of grass of the lawn 20 with an aft grass comber 520carried by the body 100 rearward of the cutter 200 and/or the drivesystem 400. In some examples, the method includes one or more of thefollowing steps: step S80 of continuously scanning for an absence oflawn 20 with a lawn detector 330 carried by the body 10, where the drivesystem 400 redirects the robot 10 in response to detecting an absence oflawn 20; step S90 of continuously scanning for a body of liquid 1004Cproximate the robot 10 with a liquid detector 350 carried by the body100, where the drive system 400 redirects the robot 10 in response todetecting a body of liquid 1004C; step S100 of continuously scanning fora potential obstacle proximate the robot 10 with a proximity sensor(e.g. infrared sensor) carried by the body 100, where the drive system400 redirects the robot 10 in response to detecting a potentialobstacle; and step S110 of continuously scanning for a boundaryresponder 600 with a boundary detector 1500 carried by the body 100,where the drive system 400 redirects the robot 10 in response todetecting a boundary responder 600.

A configuration and height of the bumper 110, in some instances, arearranged according to a ground clearance or a cut height of the cutter200. The bumper height may be lower than the cut height of the cutter200. Also, the bumper 110 may rise and lower with the cutter 200.

In one example, the drive system 400 includes left and right drivenwheels, 410 and 420 respectively, and a trailing wheel 430 (e.g. acaster). In one implementation, the drive system 400 includes at leastone drive wheel 410, 420 rotated by a motor or other drive mechanism(e.g. an electric motor supplied power from a consumer-level battery,fuel cell, large capacitors, microwave receiver, an internal/externalcombustion engine powered by an onboard fuel source, hydraulic/pneumaticmotor powered by an above aforementioned power source, large potentialenergy sources such as wound or compressed springs such as in hydraulicor pneumatic, vacuum accumulators, flywheels, or compressed air). Insome instances, the drive system 400 includes a differential drive on acenter axis 105 with two independently driven wheels 410, 420. One ormore of the wheels 410, 420, 430 may swivel to aid navigation oradjustment of yaw of the robot 10. In other implementations, the drivesystem 400 includes a holonomic drive, particularly in combination witha body 100 having a shape of constant width. The robot 10 may rotateabout more than one point within an area defined by an outline of thebody 100, thereby escaping from, traversing, or otherwise avoidingentrapment in spaces approaching a width of the robot 10.

Typically, the robot 10 is used on a yard or lawn 20. Referring again tothe example of FIG. 1A, as the robot 10 mows the lawn 20, an uncut area22 is generally longer than a cut area 24. After mowing an initial swath23, which may be linear, circular, or some other geometry, the robot 10follows a swath edge 26 (i.e. the boundary edge between the uncut andcut areas, 22 and 24 respectively) for each successive swath 23. If theinitial swath 23 is circular or arced, the robot edge following willresult in an emergent spiraling path. If the initial swath 23 is linear,upon reaching the end of a swath 23, the robot 100 rotates approximately180 degrees, aligns itself with the swath edge 26 using the cut edgedetector 310, and proceeds to mow another swath 23. The robot 10successively repeats this process until it determines that it hascompleted mowing the yard 20, for example, or until it reaches someother state which ends a mowing cycle. By aligning itself to theimmediately preceding mowed swath 23, the robot 10 may ensure that itmows the lawn 20 in a generally uniform pattern of adjacently cut swaths23, achieving a mowed appearance similar to a lawn 20 mowed byconventional devices. By relying on the cut edge detector 310 tocontinuously realign the robot's heading based as it mows eachsuccessive adjacent swath 23, the robot 10 may forgo using other morecomplex equipment for alignment, such as GPS, triangulation, inertial,and odometric reckoning, requiring additional sensors and/or processingpower.

Each of the examples shown in FIGS. 1-4 share relatively large diameterdifferential drive wheels 410, 420 (e.g., 8 inches or greater), casters430, 440 of a lesser diameter, and optional fore and aft grasscombers/lifters, 510 and 520 respectively.

FIGS. 2A-C depict alternative implementations of the lawn care robot 10having a substantially pentagonal shape of constant width in which thewidest portion trails the center axis 105. Each robot 11, 12 includes adifferential drive off, near to, or on the center axis 105 and anasymmetrical reciprocal cutter 200A. Separate edge following sensors 310and grass character sensors 320 are provided in pairs (although only oneof each is optional). FIGS. 2A and 2B also illustrate alternativelocations of the fore and aft grass combs, 510 and 520 respectively, andthe calibration sensors 320. A caster 430 or fixed bearing auxiliarywheel 440 may depress the grass. Example locations of the grassdepressing wheel 430, 440 include forward or rearward of one cut edgedetector 310, forward of a first cut edge detector 310 and rearward of asecond cut edge detector 310 (shown between in FIG. 2A), forward of thecutter 200 (shown ahead in FIG. 2B), and rearward of the cutter 200.

Referring to FIG. 2A, a robot 11 (which is configured as the robot inFIG. 33) includes one trailing caster 430 and a cutter 200A carried bythe body 100. The cutter 200A has a blade extending to an uncut side 101edge of the robot 11. A fore grass comber 510 carried by the body 100 isshown with a relatively larger front to back size to accommodate arotating bar bearing strings, filaments, chains, tines, bristles,flexible flaps, or a combination of these. The fore grass comber 510 isshown optionally laterally adjacent a grass depressing wheel 440 carriedby the body 100. One edge following sensor 310 and grass charactersensor 320 pair is carried by the body 100 and located forward of thefore grass comber 510, aligned parallel to a center axis 105, andlaterally in-line with each other. A second edge following sensor 310 iscarried by the body 100 and located rearward of the fore grass comber510, but forward of the cutter 200A.

Referring to FIG. 2B, a robot 12 includes a body 100 carrying twoleading flattener wheels 440 located forward of an edge following sensor310 and a cutter 200A that extends to a cut side 102 edge of the robot12. The edge following sensor 310 is located rearward of a fore grasscomber 510 carried by the body 100, but forward of the cutter 200A. Agrass character sensor 320 is carried by the body 100 and locatedforward of the fore grass comber 510. In this example, the edgefollowing sensor 310 is not laterally in-line with the grass charactersensors 320. A trimmer 220 is carried by the body 100 on a differentside from the edge sensor 310 and/or cutter 200A. One of the leadingflattener wheels 440 (e.g. casters) may depress the grass ahead of acut-portion span 312 of the edge sensor 310, or immediately ahead of it(e.g., separated in the moving direction by less than a cut grass heightor about two inches).

Referring to FIG. 2C, a robot 13 includes a body 100 having asubstantially pentagonal shape of constant width in which the widestportion leads a center line 105, with a drive differential substantiallyon the center axis 105 connecting left and right drive wheels 410 and420 respectively. A leading caster 440 and a trailing caster 430 areeach carried by the body 100. Three reciprocal cutters 200B are disposedon the body 100 at different front-to-back locations that overlapserially in cut width. An extended one-piece grass sensor array 315 islocated forward of a fore grass comber 510 and includes edge followingsensors 310 and grass character sensors 320. A trimmer 220 may becoupled to the body 100 either of the uncut or cut sides, 101 and 102respectively. A drive wheel 420 may depress the grass in a narrowportion following the cut-portion span 312 of the cut edge sensor 310(i.e., no grass comber follows at least this wheel).

FIG. 3A is a schematic diagram illustrating another exemplary lawn carerobot 14 having a substantially circular shape. The body 100 carriesdifferential drive wheels, 410 and 420 respectively, substantially onthe center axis 105, one leading caster 430, and three differentrotating multi-“exacto” Bellinger blade cutters 200B (as used in U.S.Pat. No. 3,550,714, although with a guard to cover the blades when thecutter 200B is not rotating, and optionally powered by separate motors).The three rotary cutters 200B are placed at different front-to-backlocations with overlapping cut widths. The arrangement of the cutters200B shown (i.e., diagonally) is amenable for either reciprocal cutters200A or rotating cutters 200B, or counter rotational shear. An edgefollowing sensor 310 disposed on the body 100 includes a fore edgesensor bank 3102 preceding an aft edge sensor bank 3104 in the directionof cutting to provide auxiliary positional input for determining whetherthe robot 14 is proceeding linearly. For example, if the fore cut edgesensor 3102 and the trailing edge sensor 3104 are aligned along a singleline parallel to the forward direction of travel of the robot 14 andboth indicate the presence of the cut edge 26, the robot 14 maydetermine that it is traveling substantially linearly. However, if onlyone of the cut edge sensors 3102, 3104 indicates the presence of the cutedge 26, the robot 14 may have deviated from a straight line path. Morecomplex interpretation and error-detection is also possible. The leadingsensor 3102 may be wider or narrower than the trailing sensor 3104 andis optionally placed on an extending or extended arm 3106 as shown. Atrimmer 220 may be coupled to the body 100 either of the uncut or cutsides, 101 and 102 respectively. The fore grass combers 510 may bereplaced with fan blades for drawing up the grass with air flowconcentric with the rotating cutters 200B.

FIG. 3B is a schematic diagram illustrating a layout of anotherexemplary lawn care robot 15 having a rectangular shape. The robot 15includes a body 100 carrying differentially steered drive wheels 410 and420, respectively, located near rear corners of the body 100, and twoleading casters 430, located near forward corners of the body 100.Differential steering allows fast yaw rates. Wheels 410, 420, 430located at the corners of the rectangular body 100 allows for goodapproach/departure angles and stability. The robot 15 also includes acutter 200, a battery 160, edge detectors 310, calibrators 320, andboundary detectors 1500, all carried by the body 100. Front and rearbumpers 110A and 110B, respectively, are secured to the body 100 and maybe configured to detect contact. Tight spacing between the wheels 410,420, 430 and the cutter 200 allow for reasonable anti scalping. Theturning center 150 is located between the drive wheels 410 and 420,respectively. The component layout and body configuration allow therobot 15 to cut up to boundaries and walls and is likely more efficientthan a skid steer configuration (shown in FIG. 3D), but may havedifficulty cutting to a 90 degree edge. The robot 15 is less likely todamage turf 20 while turning. Drawbacks to the component layout and bodyconfiguration of the robot 15, as shown, include not being able to turnin place, requiring bumper protection for all areas for and aft of thedrive wheels 410 and 420, respectively, and needing slightly less than 2times its length to turn 360 degrees (48″-60″). The robot 15 is stable,but transfers about 20% of its weight fore and aft as well as left andright at about 30 degree slopes, which causes difficulty or inability tonavigate 30 degree slopes in reverse due to traction loss and drift. Aforward center of gravity creates enough inertia to generate wheel slipin wet grass on flat terrain during edge following. The traction lossresults in a change in robot heading or drift, which may affect edgefollowing even on flat terrain.

FIG. 3C is a schematic diagram illustrating a layout of anotherexemplary lawn care robot 16 having a shape of substantially constantwidth. The robot 16 includes a body 100 carrying differentially steereddrive wheels 410 and 420, respectively, located near rear corners of thebody 100, and a leading caster 430, located on a forward portion of thebody 100. The robot 16 also includes a cutter 200, a battery 160, edgedetectors 310, calibrators 320, and boundary detectors 1500, all carriedby the body 100. Front and rear bumpers 110A and 110B, respectively, aresecured to the body 100 and may be configured to detect contact. Tightspacing between the wheels 410, 420, 430 and the cutter 200 allow forreasonable anti scalping. The turning center 150 is located between thedrive wheels 410 and 420, respectively. The component layout and bodyconfiguration allow the robot 15 to cut up to boundaries and walls aswell as cut to a 90 degree edge. The robot 15 is not likely to damageturf 20 while turning. The robot 15 is stable, but transfers about 20%of its weight fore and aft as well as left and right at about 30 degreeslopes, which causes difficulty or inability to navigate 30 degreeslopes in reverse due to traction loss and drift. A forward center ofgravity creates enough inertia to generate wheel slip in wet grass onflat terrain during edge following. The traction loss results in achange in robot heading or drift, which may affect edge following evenon flat terrain.

FIG. 3D is a schematic diagram illustrating a layout of anotherexemplary lawn care robot 17 with skid steering. The robot 17 includes abody 100 carrying differentially steered left and right drive wheels 410and 420, respectively, located near front and rear corners of the body100. To turn, the robot 17 may lock one or more wheels 410, 420 whiledriving the others. The robot 17 also includes a cutter 200, a battery160, edge detectors 310, calibrators 320, and boundary detectors 1500,all carried by the body 100. Front and rear bumpers 110A and 110B,respectively, are secured to the body 100 and may be configured todetect contact. Tight spacing between the wheels 410, 420, 430 and thecutter 200 allow for reasonable anti scalping. The turning center 150 islocated substantially near the center of the robot 17. The componentlayout and body configuration allow the robot 17 to cut up to boundariesand walls, but may have difficulty cutting to a 90 degree edge. Therobot 17 can turn on its center. Four wheel drive reduces the need for alow center of gravity and offers excellent step and hill climbingability. A 50-50 weight distribution limits the occurrence of drift onslopes.

FIGS. 3E-H are block diagrams depicting typical control electronics andinstrumentation which may apply to any appropriately similar robotdescribed herein. FIGS. 3E and 3F are block diagrams suitable for arobot 10 with differential steering and an oblong “tombstone” form.Essentially the same components may be used in any of the differentiallysteered robots disclosed herein. As shown in FIGS. 3E and 3F, a bumper110 is connected to left and right bump sensors 110L and 110R,respectively, at each of front and rear ends. These permit the robot 10to detect the direction of a bump using the timing of actuation (e.g.,if the left front is actuated before the right, an obstacle is forwardand to the left). The controller 450 in main electronics 5400 can usethis direction to back and turn the robot 10 away and angled away fromthe side of detection. Hard surface detectors 330E as discussed herein(one method of determining a lack of grass) are placed at all fourcorners of the robot 10 and monitored by the controller 450. Artificialboundary (VF—Virtual Fence) detectors 529 as disclosed herein are alsoplaced at all four corners of the robot, monitored by the controller450. Wheel drop sensors 430A are part of the wheel assemblies of caster430 and left and right drive wheels 410 and 420, respectively, monitoredby the controller 450. Detections on bump, wheel drop 462A, hard surface330, and VF boundary 529 sensors are activating conditions for obstacleavoidance behaviors and/or obstacle following behaviors (“behaviors” inthe context of behavior based robotics) as disclosed in U.S. Pat. No.6,809,490, as well as those behaviors disclosed in U.S. PatentApplication No. 20070016328 for “Autonomous surface cleaning robot forwet and dry cleaning” to Ziegler et al., herein incorporated byreference in its entirety.

FIGS. 3E and 3F further show encoders 430B provided to each wheelassembly 410, 420, 430, which are monitored together with bumps andmotor currents by the controller 450 to register a stuck condition(stasis), an activating condition for escape behaviors as disclosed inU.S. Pat. No. 6,809,490. Similarly, a cutter motor assembly 202 isprovided with an encoder for detecting jams and speed. Right and leftcut edge sensors 310 as described herein in various forms (310A, 310B .. . 310X) are provided and employed by the controller 450 as describedherein. A wireless transceiver 55 communicates with the controller 450(interchangeably controller 5400) to permit the wireless remote to sendand/or receive signals. A user interface 5410 (e.g., display paneland/or buttons) controlled from the controller 450 permits statussignals and instructions. A manual mode interface 5411 is as describedherein with reference to mounting, dismounting, and folding handles(e.g., permitting dead man and other signals to be switched, and handlestatus detected), for manual and autonomous modes.

FIGS. 3E and 3F differ primarily in that FIG. 3E is primarily powered byan internal combustion engine 5451 (which may directly drive somecomponents via clutches and/or transmissions, and may also drive analternator or generator for powering devices or charging a battery 5454to do the same). FIG. 3F is primarily powered by a battery 5501 (whichpowers, e.g., brushless or other DC motors via motor control circuitsand motor amplifiers). An internal combustion engine is primarilyselected for energy density and rapid cycle times (e.g., replacing fuelis faster than recharging a battery), and need not be used to directlydrive a cutter 200.

It should be noted that a feature of the both internal combustion andbattery powered arrangements is that when the robot 10 is placed inmanual mode, clutches on the driven wheels (in some instances not shown,but all driven wheels disclosed herein may be clutched for this purpose)disengage wheels that are driven in autonomous modes, providing morepower for manual mode. In each case, the controller 450 may, in responseto the detection of manual mode (optionally in association with thehandle being attached or unfolded), activate a high power mode for thecutter 200 (the cutter motor, gearbox, clutch, and cutting elementstrength being selected to accommodate this greater stress mode). Thisis appropriate for instances in which the user believes or perceives therobot 10 may be overmatched by lawn growth. An additional feature isthat the wireless transceiver 55 may be used to activate a “normallyoff” switch connected to the ignition of an IC motor or motor currentloop on an electric motor. When the robot 10 is out of range or unableto receive wireless signals from of a wireless remote that broadcasts a(continuous or interval of seconds to minutes) dead man signal, therobot 10 will be deactivated—and may be remotely deactivated by stoppingthe dead man signal.

The battery powered robot 10 of FIG. 3F is controlled as discussedherein with respect to the included schematics and control diagrams. Theinternal combustion motor robot 10 of FIG. 3E includes engine monitoringand control (ECU) 5402 for monitoring the state of the motor 5451.Various sensors, including voltage and current states as well asconventional sensor configurations, may be connected to the ECU 5402,including some or all of intake air pressure and temperature, barometricair pressure, coolant temperature, throttle position, crank position,cam position, fuel injection start angle and pulse width, and sparkadvance. Fuel level, ignition status, kill switch status, and dead-manswitch status may be monitored by the ECU 5402 or main controller 450 or5400. The motor 5451 powers a generator 5452, via a conventional gearboxor other transmission. If the gearbox is fully backdriveable or withappropriate gear ratios, the generator or alternator 5452 may beconfigured to act as a starter motor (with appropriate circuitry). Powerconditioning 5404 turns the output of the generator 5452 into smoothed,less noisy, and optionally DC current for charging batteries and drivingelectric motors. The battery 5454 may be connected for electric start ofthe IC motor 5451 for powering electric motors in left wheel assembly410, right wheel assembly 420 (if these are not directly driven), andfor powering main electronics 5400 and wireless transceiver 55. Dead mansignals or switches (normally off), or kill switches (normally on) asdescribed herein are connected to leave the main electronics 5400 andwireless transceiver 55 powered even when the robot 10 is immobilized orunable to cut by disabling ignition, fuel supply, air supply, normallydisengaged or normally engaged clutches, or motor current loops. Theinternal combustion motor robot 10 of FIG. 3E includes a clutch 5453 andcorresponding actuator (e.g., solenoid, motor, or EM) intermediate theIC motor and the cutter 200 itself. The clutch 5453 disengages the ICmotor from a mechanically powered (via a transmission such as a belt,shaft, chain, or gearbox) cutter 200, or disengages an electric motor(not shown) from an electrically powered (via the generator 5452) cutter200.

FIGS. 3G and 3H are block diagrams depicting typical control electronicsand instrumentation which may apply to any appropriately similar robotdescribed herein, but are particularly suited for an articulating“skidder” configuration. Those elements that have like numbers aselements in FIGS. 3E and 3F have substantially the same structure andfunction.

Contrasting FIG. 3F to FIG. 3H, the skidder or pivoting configuration(rather than having a single forward caster) includes left and rightpassive wheel assemblies 5210. Each of these includes a drop sensor 430Aand encoder 430B monitored by the controller 450 or main electronics5400. An articulating pivot 5305 as described herein separates the body18 into two parts. The pivot 5305 includes a slip ring or flexible wireharness for passing wiring from the first portion 5100 to the secondportion 5200 of the body 5000. A (preferably electric motor) pivotactuator 5310 is controlled by main electronics 5400, and the pivot 5310position is monitored by an absolute encoder (i.e., one which returns anabsolute position rather than relative position). A main drive wheel5110 is powered by a motor assembly 5455.

Many of these same differences are found in contrasting the ICconfiguration of FIG. 3E to the IC skidder configuration of FIG. 3G. TheIC skidder configuration as shown includes two clutch configurations. Adrive clutch actuator and clutch 5452 disengages the IC motor 5451 froma mechanically powered (via a transmission such as a belt, shaft, chain,or gearbox) main drive wheel 5110 or disengages an electric motor (notshown) from an electrically powered (via the generator 5452) main drivewheel 5110. A cutter clutch actuator and clutch 201 disengages the ICmotor 5451 from a mechanically powered (via a transmission such as abelt, shaft, chain, or gearbox) cutter 200, or disengages an electricmotor (not shown) from an electrically powered (via the generator 5452)cutter 200. These and other clutches disclosed herein may be engaged ordisengaged for manual mode in stability situations (e.g., using a tiltsensor the controller determines that the robot should be immobilizedand engages clutches appropriately) or when an E-stop, dead-man switchor signal, or kill switch or signal is used. The controller 450 may alsoengage and disengage clutches during escape behaviors.

FIG. 3I depicts connections between electronic components and is one wayof connecting components as set forth in FIG. 3G and herein below. FIG.3I is different from FIG. 3G at least in that all of the motors fordrive, pivot, and cutting are electric; and that the two front wheelsare each driven. Steering motors 5456 on left and right forward sidesare connected (including motor control and amplification) to the controlboard 5400. An articulation (pivot) motor 5310, a main drive motor 5455,and a payload or cutter motor 202 are similarly connected (includingmotor control and amplification). Power conditioning 5404 includes acharging or recharging circuit for the battery (one or two circuits mayconvert IC motor/alternator AC and/or household AC to charge thebattery), conditioning for the IC motor/alternator AC current to smoothand remove noise using inductors or the like, and a starting circuit forproviding starting current (in appropriate AC or DC form, voltage, andcurrent) to the starter and/or alternator. The starter and alternatormay be the same or different devices. Both a kill switch K and a deadman switch D intervene between the ignition and the IC motor 5451 (e.g.,in a manner to damp or short ignition functions). Each can be activatedby the control board 5400 and robot behaviors and also directly bymanual switches, relays, or the like provided on the robot body orattachable/foldable handle.

FIGS. 3J and 3K show block component layouts of some of the componentsdiscussed with reference to FIGS. 3G and 4A-N below. Payload and payloadmotor 202 are usually near the ground (in order to carry out lawn care),shown in the middle of the robot. Steering and articulation motors(electrical) 5456 and 5310 are placed essentially adjacent the wheels orpivot to be controlled. However, as shown in FIGS. 3J and 3K, at leasthalf (three components of, in this case, six components) of the heaviestcomponents that may be placed in different locations—an IC engine 5451,alternator/generator 5452, drive motor 5455, battery 5454, controlelectronics board 5400 (if more than one board, the heaviest ones ofthese), and fuel tank 5458—are positioned at least in part below thecenter axis of the highest diameter driven wheel (here main drive wheel5110) in order to lower the center of gravity. It is not necessary forthese components to be placed within the volume of the highest diameterdriven wheel 5110 in order to be below the center axis of it. However,as shown in FIGS. 3J and 3K, it is preferable to place at least half ofthese six components within the volume of the highest diameter drivenwheel. In FIG. 3J, the IC engine 5451, alternator 5452, drive motor5455, battery 5454, and fuel 5458 are within the volume of the highestdiameter driven wheel and the control electronics board 5400 is placedwithin the main body but outside the volume of the highest diameterdriven wheel. In FIG. 3K, the control electronics board 5400, drivemotor 5455, and battery 5454 are within the volume of the highestdiameter driven wheel, but the IC engine 5451, alternator 5452, and fuel5458 tank are placed within the main body but outside the volume of thehighest diameter driven wheel. Heavy components (often the engine,motors/generators, batteries, fuel, control electronics including motoramplifiers) are used to lower the center of gravity.

Referring to FIGS. 4A-N, a robot 18 includes a body 5000 having firstand second portions 5100 and 5200, respectively, joined at anarticulated joint 5300. The first body portion 5100 defines a payloadarea 5102 that carries a controller 5400, a drive motor 5450, and apower source 5500, for example. At least one drive wheel 5110 rotatesabout an axis 5105 defined by the first body portion 5100. The outerdiameter of the drive wheel 5110 is sized to be greater than a lengthand height of the payload area 5102. In some examples, the outerdiameter of the drive wheel 5110 is about 16 inches. In one example, asshown in FIGS. 4A-D, one drive wheel 5110 defines an inner cavityhousing the payload area 5102. The first body portion 5100 includes leftand right arms 5120 and 5130, respectively, extending from the payloadarea 5102 around the at least one drive wheel 5110 to the articulatedjoint 5300. The second body portion 5200 defines an axis 5205 andcarries at least one free wheel 5210 that rotates about rear axis 5205.In some examples, the outer diameter of the free wheel 5210 is about 9inches and the robot 19 has a center of gravity CG a height H from aground surface of about 3 inches. The at least one free wheel 5210 maypivot about an axis perpendicular to the rear axis 5205. For example,the at least one free wheel 5210 may pivot laterally with the pivot axisparallel to a direction of travel, allowing the second body portion 5200to lean into turns.

The articulated joint 5300 includes an actuator 5310 (e.g. a motor andgearbox) controlled by the controller 5400 and configured to rotate thefirst and second body portions 5100 and 5200, respectively, in relationto each other about at least one pivot 5305 of the articulated joint5300. In some examples, as shown in FIG. 4B, the articulated joint 5300allows the second body portion 5200 to twist relative to the first bodyportion 5100 about a drive direction. In some examples, as shown in FIG.4D, the articulated joint 5300 rotates a drive direction of the firstbody portion 5100 an angle A of between about +90° and about −90° withrespect to a drive direction of the second body portion 5200. Thisallows the robot 18 to pivot 360° about a free wheel 5210.

FIGS. 4E-G illustrate an example of robot 18 with two drive wheels 5110carried by the first body portion 5100. The configuration shownpartially exposes the payload area 5102 between the two drive wheels5110. The two drive wheels 5110 may be driven independently from eachother.

Referring to FIGS. 4H-I, the robot 18 may be driven with the first bodyportion 5100 leading the second body portion 5200 and vice-versa. Therobot 18 includes at least one lawn care unit 5600 carried by the firstand second body portions 5100 and 5200, respectively. In the exampleshown, the robot 18 includes lawn care units 5600A and 5600B carried bythe first body portion 5100 and lawn care unit 5600C carried by thesecond body portion 5200. When the robot 18 is configured to have thefirst body portion 5100 leading the second body portion 5200, lawn careunit 5600A may be configured as a cutter 200, lawn care unit 5600B maybe configured as a grass comber 510, 520 and/or a cut edge detector 310,and lawn care unit 5600B may be configured as a cutter 200. When therobot 18 is configured to have the second body portion 5200 leading thefirst body portion 5100, lawn care unit 5600A may be configured as acutter 200, lawn care unit 5600B may be configured as a cut edgedetector 310, and lawn care unit 5600B may be configured as a grasscomber 510, 520 and/or a cut edge detector 310.

Referring to FIGS. 4J-N, in some examples, the drive wheel 5110 issupported by the first body portion 5100 on three roller supports 5112,each positioned about 120° from the other. A drive pinion 5114 coupledto a motor 5450 by a transmission 5455 drives the drive wheel 5110. Thedrive wheel 5110 has a relatively low center of gravity CG-W. In someinstances, the drive wheel 5110 defines a stepped profile, as shown inFIG. 4K. In other instances, the drive wheel 5110 defines a truncatedprofile with a sharp peak, as shown in FIG. 4L. In other instances, thedrive wheel 5110 defines a knobbed profile, as shown in FIG. 4M. Inother instances, the drive wheel 5110 defines a treaded and/or curvedprofile, as shown in FIG. 4N.

Referring to FIGS. 5A-B, a rotary cutter 2000 includes upper and lowerdisk guards 2010 and 2012, respectively, and first and second cutterblades 2013 and 2014, respectively, disposed between the upper and lowerdisk guards 2010 and 2012, respectively. The rotary cutter 2000, in someexamples, includes first and second blade tip guard combs 2015 and 2016,respectively, disposed on corresponding the first and second cutterblades 2013 and 2014, respectively. The blade tip guard combs 2015, 2016reduce blade injuries and comb the grass 20. An optional blade lock 2017holds the first and second cutter blades 2013 and 2014, respectively,together to form one rotating cutter.

In some implementations, the robot 10 includes an aerator or erectorwhich lifts cut grass 24, thereby adding perceived volume to the mowedlawn 24 and enhancing an aesthetic appearance of the lawn 20. Theaerator/erector may include an active brush or comb for brushing thegrass upward, for example. The robot 10 may include an aeration and/orlift system as disclosed in U.S. Pat. No. 6,611,738; US PatentApplication Publication 2004/0187457; and/or U.S. Pat. No. 3,385,041,all incorporated herein by reference in their entireties.

In some instances, the surface treater 200 includes sheep shear-style orhedge-trimmer-style cutters 200A, which confine their cutting action toa particular radius and prevent objects greater than that radius frombeing accidentally cut. For example, the size of the cutting radius maybe selected to be smaller than a child's fingers or toes, so as toprevent accidental injury. Moreover, the cutter 200 cuts with asubstantially low energy rate of approximately 70 watts over a 0.5 metercutting length. The rate of energy expenditure is low enough that therobot 10 can run for a sufficient period of time to cut a yard oftypical size.

FIG. 5C is a schematic view of a simplified reciprocating cutter 2050 asan example of a reciprocating cutter 200A. The sickle-bar cutter 2050includes first and second blades, 2051 and 2052 respectively, positionedparallel to each other and moved in opposite reciprocating motions by anactuator 2060.

Referring to FIGS. 5D-E, a reciprocating cutter 2050 includes a housing2055 carrying an arm 2070 positioned to rotate horizontally (e.g. fromright to left and back) with regard to the lawn about a pivot bearing2072. A cutting blade 2080 is mounted to an external end of the arm 2070and abuts a comb 2084 connected to the housing 2055. The spinning motionof a driven shaft 2076 is translated into reciprocating side-to-sidemotion for the arm 2070 via the eccentric bearing 2074. As the arm 2070moves horizontally from side to side, the teeth 2082 of the cuttingblade 2080 shearingly slide horizontally while in contact with the tines2086 of the comb 2084, cutting any blades of grass caught in grooves2085 formed between the adjacent cutting blade 2080 and comb 2084. Inone example, the distance of reciprocation is five centimeters or less(i.e., of the blade 2080 with respect to the comb 2084).

Referring to FIG. 5F, the reciprocating cutter 2050 includes a bladetensioner 2090 providing evenly-spaced downward tension on the cuttingblade 2080. The teeth 2082 of the cutting blade 2080 are even urgedagainst the comb 2084, enhancing the shearing action. The bladetensioner 2090 may include one or more arched extensions extending fromthe arm 2070. Alternatively, the blade tensioner 2090 may include aseparate unit connected to the body 100, such as a heavyhorizontally-aligned bar that provides a downward pressure against thecutting blade 2080.

Referring to FIG. 5G, the reciprocating cutter 2050 includes two cuttingblades 2080A and 2080B, each actuated by separate arms 2070A and 2070B,respectively, reducing the number of teeth 284A, 284B on each cuttingblade 2080A and 2080B, respectively.

The cutting blade 2080 may include four teeth 2082 per every five combtines 2086. Alternatively, the cutting blade 2080 may include nine teeth2084 per every ten tines 2086. The cutting blade 2080 and comb 2084 mayfunction such that only one (or alternatively, two) teeth 2082 arecutting at a time during operation of the cutter 2050. The teeth 2082 ofthe cutting blade 2080 and the tines 2086 of the comb 2084 may havemutually different pitches and may be chamfered. The number of teeth2082 or tines 2086 may be a multiple of the number of teeth present in atypical sheep-shearer; for example, three times the factor of wideningof the comb 2084 with respect to the sheep-shearer. The clamping forceprovided to the blade 2080 against the comb 2084 may be uniform, or mayvary across the horizontal area of the blade 2080, within a range ofacceptable clamping force. The material of the cutting blade 2080 and/orcomb 2084 may include hardened metal (such as steel) which is stamped,molded, then machined, forged, and machined again.

The comb 2080 and/or cutting blade 2084 may include mounting holes formounting the cutting blade 2080 or comb 2084 to a yoke. The teeth 2082or tines 2086 may have rounded tips to guide blades of grass into thegrooves 2085. The spacing of the teeth 2082 or tines 2086 may beestablished to optimize the opening gap 2085.

The curves of the blade 2080 and comb 2084 may have outlines similar tothose of a sheep-shearing device when the radius is nine inches or less;when the radius of curvature thereof is greater than nine inches, thecurves of the blade 2080 and comb 2084 may be altered in accordance withthe driving radius and cutter radius.

Referring to FIG. 5H, a cutter 2100 includes a first blade 2110 mountedto and rotatably driven by a motor 2140. A second blade 2110 is mountedto and rotatably driven by a planetary gearbox 2130 driven by the motor2140. The first and second blades 2110 and 2120, respectively, rotate inopposite directions to shear grass. The cutter 2100 has the liftcapabilities of a conventional rotary cutter, but requires less power tooperate and generally provides a cleaner cut. In some examples, thesecond blade 2110 is either fixed or free floating, rather than drivenby a planetary gearbox 2130. In the fixed second blade configuration,only the first blade 2110 rotates thereby shearing grass with a scissortype action.

Referring to FIG. 5I, a cutter 2200 includes a cutter frame 2210defining a longitudinal axis 2215. The cutter frame 2210 is mounted tothe body with the longitudinal axis 2215 substantially parallel to aground surface. A driven wire holder 2220 is rotatably mounted to thecutter frame 2210 to rotate about the longitudinal axis 2215. The wireholder 2220 includes a plurality of spaced disks 2222 and at least onewire 2224 secured near a peripheral edge of the disks 2222 and arrangedsubstantially parallel to the longitudinal axis 2215. The rotating wireholder 2220 and associated wire(s) 2224 cuts grass with relatively lesspower than a conventional rotary cutter.

In some examples, the surface treater 200 includes a fertilizer orpesticide dispenser for distributing fertilizer or pesticide over theyard 20, either in lieu of or in addition to other lawn care tasks suchas mowing.

Referring to FIGS. 6A-B, the robot 10 generates electrical power whichmay be stored. One implementation utilizes a generator 1702, such as adc motor that spins to generate DC current. Control often involves avoltage regulator 1704 to prevent high and low voltages in the system.Another implementation includes an alternator. An alternator is a threephase generator that is run through a set of diodes to rectify the ACcurrent to DC. With the use of an additional voltage regulator it ispossible to get stable, nearly ripple-free DC current from thealternator.

FIG. 6A illustrates a hybrid mechanical-electric system 1700A includinga fuel source 1702 delivery fuel to an engine 1704 that drives a cutter1706 and a generator 1708. The generator 1708 is connected to a voltageregulator 1710. The voltage regulator 1710 is connected to an energystorage unit 1712 (e.g. a battery), a drive motor 1714 and electronics1716.

FIG. 6B illustrates an all electric system 1700B including a fuel source1702 delivery fuel to an engine 1704 that drives a generator 1708. Thegenerator 1708 is connected to a voltage regulator 1710. The voltageregulator 1710 is connected to an energy storage unit 1712 (e.g. abattery), a drive motor 1714, a cutter 1706, and electronics 1716.

Referring to FIGS. 6C-D, the robot 10 includes six different categoriesof components; each of which performs a narrow function of total systemoperation. The six categories include: C1) Fuel—Storage and delivery offuel to the engine; C2) Intake—Passage of air into the engine; C3)Engine—Combustion of fuel to create mechanical work from stored energy;C4) Electrical Output—Components to create usable electrical power fromshaft work; C5) Starting—Components to start the engine; and C6)Mechanical Output—Components designed to channel shaft work toappropriate locations. For each of the six categories, there are threeseparate types of components: required (minimum complexity (cost) pathto operation), optional (these components will add additional featuresor functionality to the product at additional cost, and expected.

FIG. 6E provides a schematic view a neighborhood 1000 including houses1002, grass-cutting obstacles 1004 (e.g. trees 1004A, bushes 1004B, andwater 1004C), boundaries 1006 (e.g. fences 1006A and property lines1006B), non-cuttable areas 1008 (e.g. driveways 1008A, sidewalks 1008B,and roads 1008C), and cuttable areas 1020. Although a fairly simpleneighborhood 1000 is shown, the depiction is sufficient forsubstantially topologically equivalent, less linearly oriented lawns, orlawns with islands, multi-section lawns, and or other discontinuities.

The delineation between areas intended to be traversed by the robot 10and areas not intended to be traversed by the robot 10 may be dividedinto different types of boundaries, including visible boundaries andinvisible boundaries, natural boundaries, artificial boundaries,arbitrary, political boundaries, navigable and blocking boundaries. Lawnedges are a type of arbitrary boundary that abut many kinds of non-grassor non-mowable areas (e.g., fences, flowerbeds, gardens, mulch,sidewalks, walls, steps). Arbitrary boundaries also include boundariesestablished for property or other reasons within a physically mowablecontinuous grass area. Examples of arbitrary boundaries include aboundary between a bed of azaleas (bedded in tree-bark mulch) and agrassy lawn and a boundary between a grassy lawn and a concretedriveway. The transition between the grass and non-grass area, or thenon-grass area itself, is discernable by virtue of differing physicalproperties. In many cases, the difference is visually discernable.However, the robot 10 uses a limited set of less complex physicalcharacteristics, such as average reflected wavelengths of light (i.e.,color) or mowing resistance (correlating to grass presence).

The arbitrary boundaries which are not readily ascertainable bydifferences in physical characteristics include property lines 1006Bbetween adjacent lots in a neighborhood 1000 and a border between afirst yard region 1020 which should be mowed and a second yard region1020 which should not be mowed due to seeding, damage, or the like. Torecognize the arbitrary boundaries, the robot 10 uses boundaryresponders 600, such as lengths of identifiable cord (“cord” alsomeaning wire, tape, chain, or cord of discrete elements in a boundedline).

FIGS. 7A-7E depict structures relevant to switching between autonomousand manual operation of the robot 10. FIGS. 7A, 7C-7F depict structuressuitable as an analog of a conventional push mower handle.

FIGS. 7A and 7B are schematic views of methods of navigating a lawn carerobot 10. Referring to FIG. 7A, one method of manually leading the robot10 includes using an IR or wireless remote 50 that sends a signal to areceiver 55 on the robot 10. The drive system 400 is configured tofollow the signal received from the remote 50

Another method includes guiding the robot 10 with a push bar 116attached to the body 100. The push bar 116 may be detachable from orstowable on the body or housing 100. For example, if the robot 10 isprogrammed to avoid thick vegetation so as not to become mired orentangled, an operator may nonetheless override the behavior by guidingthe robot 10 with the push bar 116. In some cases, the push bar 116includes a switch, speed setting, or joystick to advance and steer therobot 10. In one instance, the push bar 116 includes one or morepressure or strain sensors, monitored by the robot 10 to move or steerin a direction of pressure (e.g., two sensors monitoring left-rightpressure or bar displacement to turn the robot 10). In another instance,the push bar 116 includes a dead man or kill switch 117A incommunication with the drive system 400 to turn off the robot 10. Theswitch 117A may be configured as a dead man switch to turn off the robot10 when a user of the push bar 116 ceases use or no longer maintainscontact with the push bar 116. The switch 117A may be configured act asa kill switch when the push bar 116 is stowed, allowing a user to turnoff the robot 10. The dead man or kill switch 117A may include acapacitive sensor or a lever bar. In another instance, the push bar 116includes a clutch 117B to engage/disengage the drive system 400. Therobotic mower 10 may be capable of operating at a faster speed whilemanually operated by the push bar 116. For example, the robotic mower 10may operate at an autonomous speed of about 0.5 m/sec and a manual speedgreeter than 0.5 m/sec (including a “turbo” speed actuatable to 120-150%of normal speed).

Referring to FIG. 7B, in yet another method of navigating the robot 10,the robot 10 includes a pull leash or retractable lead wire 118 fedthrough a guide 120 from a spool 122. In this example, the drive system400 includes a controller 450 carried by the body 100 and controllingthe release and retraction of the spool 122. The pull wire extends for6-10 feet, for example, and the robot 10 monitors the amount ofextension directly or indirectly (encoder, etc.), as well as thedirection in which the wire is pulled (monitoring a position of the wireguide 120). The robot 10 follows the direction of the pull and controlsspeed to maintain a wire length. FIG. 7B also shows a grass erector 510carried by the body 100 forward of the cutter 200. The grass erector510, 520 includes a driven wheel 510A having an axis of rotationparallel to the lawn 20, 1020 and a plurality of flexible grassagitators 510B extending radially outward from the wheel 510A.

Referring to FIGS. 7C and 7D, robot 19 is configured for autonomous andmanual (push) modes. As shown in FIG. 7D, the handle 116 is configuredsubstantially in the form of a conventional push mower handle. Thehandle 116 includes, at an upper end, a dead man switch 117A manuallyoperable by the hand of an operator. The dead man switch 117A isconnected to a spring loaded actuator 117D and is thereafter connectedto the robot 19 using a connection line 117E (which may be a movablemechanical actuator cable or an electrical line). At a lower end of thehandle 116, the connection line 117E is passed through a connector 116Cto the robot 19. The handle 116 is connectable to the robot 19 via theconnector 116C, as well as via a brace 116B. The lower end of the handle116 is connected substantially in the neighborhood of the axis of thewheels 410, 420 at the rear of the robot 19, while the brace 116B andlower connection together permit the robot 19 to be tipped via thehandle 116 as the handle is lowered by a user. In this manner, the robot19, used in manual mode, may be tipped and turned in place in the mannerof an ordinary push mower.

The dead man switch 117 a is provided with a mechanical bias or springthat biases the switch 117 a to an “off” position. In this case, “off”means a mechanical or electrical state in which an internal combustionor electrical cutter drive cannot function. For an internal combustioncutter drive, examples of “off” include an open circuit from an ignitionor a short between a spark terminal and an engine block or other knowndevice for disabling the IC engine. For an electrical cutter drive,examples of “off” include an open circuit, normally off relay, or otherknown device for disabling an electrical motor. In either case, a brakeand/or clutch may be connected to the dead man switch 117 a and actuatedat the same time as, or instead of, disabling the motor. In an “on”position, the switch 117 a is held against the bias of the spring by theoperator. The switch 117 a may not be locked or fixed in the “on”position.

The robot 19 depicted in FIGS. 7C and 7D, capable of receiving thedetachable push/pull handle 116, has an internal combustion engine (orequivalent fuel-based or combustion system providing high energy densitysuch as fuel cells) for direct drive of a cutter, charging batteries orpressurizing fluids. The robot 19 also includes a number of electricalor hydraulic motors, including one or two drive motors 460 (driven tomove the robot forward) and/or one or two steering motors 470 (driven atdifferential rates or together to turn the robot 10). Each motor 460,470 that connects to a driven wheel is provided with an electromagneticclutch or other electrically actuated clutch to disengage the respectivemotor in manual modes. One clutch may disengage more than one motor. Theelectromagnetic clutches may be controlled from the controller 450, ormore directly via the connector 116C as discussed herein.

As shown in FIGS. 7C and 7D, the handle 116 is detachable via theconnector 116C provided to the robot and a corresponding connector 100Aprovided on the robot body 100. The connectors 116A or 100A may each bemechanical (i.e., if passing an actuating cable or transmitting itsmotion), or may be electrical (multi-pin connectors).

The connectors 116A and 100A may have additional functions. When thehandle 116 is attached, the dead man switch 117A is a normally offswitch that transmits the “off” condition (disengaging or killing thecutter drive) to the mower via the connectors 116A, and can be actuatedmanually to change to an “on” condition. However, upon removal of thehandle 116 from the robot 19, the normally “off” default condition isreversed in order to permit the robot 19 to operate autonomously (andrestored whenever the handle 116 is attached). Either or both of theconnectors 116A, 100A may be provided with a reversal switch that isactuated when the handle is removed, the reversal switch providing thesame status as if the handle 116 were attached and the dead man switch117A held by an operator. While it is possible to carry out reversalswitching in software, it is preferable that a dead man switch 117A relyon robust mechanical connections or open/closed current loops to engageand disengage the switch 117A. The reversal switch associated withconnectors 116A or 100A also preferably employs a mechanical switch oropen/closed current loop to provide the “switch on” condition.Alternatively, the reversal switch may be provided within the robot body100 rather than directly at connectors 100A, 116A.

In some implementations, the connectors 116A or 100A, or the dead manswitch 117A, are monitored by a handle sensor that detects a presence orabsence of the handle 116. The handle sensor is connected to acontroller 450, which initiates or deactivates manual mode, (e.g.,activating the clutches to disengage the drive and steering motors fromthe wheels) in response to a detected presence or absence of the handle116. Based on this detection, the controller 450 may prevent the robot19 from entering any autonomous mode while the handle 116 is attached(with the exception of a set-up or testing mode in which the robot ispushed within detection range of active or passive barriers orresponders.)

As shown in FIG. 7C, as the robot 19 is used in fully autonomous modes,the handle 116 is left hanging or otherwise conveniently stored in auser's garage or other sheltered property. The robot 19 completes thebulk of the yard mowing, or all of the mowing in segmented areas.Depending on the yard configuration, uncut areas may be bounded byobstacles, otherwise unreachable, or outside a boundary set by the user.The user may choose to complete, finish, or touch up remaining areas.Preferably, the robot's dock, home base, or finishing location is in thevicinity of the handle storage location. In any case, the user mountsthe handle 116 on the robot 19. As the connectors 116C and 100A engagemechanically, the aforementioned reversal switch is deactivated,bringing the dead man switch 117A into operation (and, as it is normallyoff, preventing cutting operations). The controller 450 of the robot 19may detect the presence of the handle 116A and enter a manual mode inresponse. Either implementation may be used by the controller 450 topower and disengage the clutches of the drive and/or steering motors,460 and 470 respectively, so that the robot 19 may be freely pushed. Inone example, the clutches are normally engaged so that a robot having adead battery or other power failure will not readily roll down a hill asthe normally engaged clutches connect the non-backdriveable orbackdriveable with resistance motors to the wheels 410, 420. The usermay then freely push the mower, pressing the dead man switch 117A tostart the motor and/or cutters 200. The robot 19 may be self-propelledin manual mode, faster than autonomous mode, and may be controlled usingthe dead man switch 117A or other manual control.

FIGS. 7E and 7F depict robot 19 with a different, foldable handlestructure and body structure, but in general similar to the detachablehandle structure of FIG. 7F. As shown in FIG. 7F, the handle 116, whilein use, remains configured substantially in the form of a conventionalpush mower handle. The handle 116 includes a dead man switch 117A with aspring loaded actuator 117D and connects to the robot 19 via aconnection line 117E (not shown). The connection line 117E is passedthrough a lower end of the handle 116 to the robot 19. The handle 116 isconnectable to the robot 19 via a pivot connector 100A on the robot 19,as well as via a sliding brace 116B. The lower end of the handle 116 isconnected substantially in the neighborhood of the axis of the wheels410, 420 at the rear of the robot 19. The sliding brace 116B and lowerconnection 100A together permit the robot 19 to be tipped via the handle116 as the handle 116 is lowered by a user. In this manner, the robot19, used in manual mode, may be tipped and turned in place in the mannerof an ordinary push mower.

A folding joint 117F or switches within the pivot connector 100A orsliding brace 116B may have the same functionality as the connectors116A and 100A, previously described. When the handle 116 is unfolded thedead man switch 117A is a normally off switch that transmits the “off”condition (disengaging or killing the cutter drive) to the mower via thepivot connector 100A, and can be actuated manually to change to an “on”condition. However, upon folding of the handle 116 flush to the robot19, generally conforming to the body 100 of the robot 19, the normally“off” default condition is reversed to permit the robot 19 to operateautonomously (and restored whenever the handle 116 is attached). Thefolding joint 117F, the pivot connector 100A, or sliding brace 116B maybe provided with a reversal switch that is actuated when the handle isfolded down. The reversal switch provides the same status as if thehandle 116 was unfolded and the dead man switch 117A held by anoperator. As shown in FIG. 7E, the dead man switch 117A may be foldeddown to a position in which it is facing up and substantially in thesame position as a useful kill switch 117C. In this position, and withthe reversal switch activated, the dead man switch 117A may becomenormally “on”, actuatable to an “off” condition, and thereby also becomea kill switch 117C.

The mower in manual mode, with the handle attached and dead-man eitheron or off, may be used in a check setup mode by the user. This checksetup mode would require the user to circumnavigate and approach allboundaries, obstacles, and marked guarded areas to be avoided by therobot. The robot, via the user interface, notifies the user upon therecognition or activation of each boundary, obstacle, or responder. Theuser would be instructed to diligently try and “fool” the robot (i.e.,manually push the robot to test, avoid, and or approach areas notclearly bound by a boundary or responder) or escape boundary confinementwithout detection, and if successful, would know to place additionalboundary segments or responders, including redundant boundary segmentsor responders as necessary. The robot may also be configured to permitautonomous mowing only after sufficient setup checking (e.g., certaindistance odometered in check setup mode).

In some examples, the autonomous robot 10 includes a not-grass detector330 to aid mowing grassy areas 20, rather than areas which should not bemowed or traversed, such as concrete, mulched or gravel-coveredsurfaces. The not-grass detector 330, in various examples, includes amechanical, electrical, piezoelectric, acoustic, optical or othersuitable sensor capable of detecting a presence of grass. Certain of thesensors discussed above with regard to the cut edge sensor 310 mayfunction as the not-grass detector 330 if arranged in a position orextending to a position other than the location of the cut edge sensor.The not-grass detector 330 and cut edge sensor 310 may be integrated orcombined as a single unit.

Referring to FIG. 8A, in some implementations, a not-grass detector 330Aincludes a chlorophyll detector having one or more light emitters 332and an optical sensor 334. The wavelengths emitted by the light emitters332 are selected based on an absorption spectrum of chlorophyll. In oneexample, the not-grass detector 330A includes four different colorednarrow-spectrum light emitting diodes (LEDs) 332A-D. LED 332A emits ablue wavelength. LED 332B emits a green wavelength. LED 332C emits ayellow wavelength. LED 332D emits a red wavelength.

The optical sensor 334 receives and analyzes light reflected from anarea illuminated 20A by the light emitters 332 to determine a presenceof chlorophyll. In some examples, the optical sensor 334 includes agray-scale or black and white (1 bit) detector. When an image providedby the optical sensor 334 is primarily dark or black (or weak signal) inresponse to blue and red light emitted by light emitters 332A and 332D,respectively, but is primarily light or white (or strong signal) inresponse to green and yellow light emitted by light emitters 332B and332C, respectively, the robot 10 determines that the illuminated area20A likely includes grass and traverses and/or mows the illuminated area20A.

FIG. 8B provides an example of signals from the optical sensor 334(i.e., filtered averaged over the area 20A) in response to fourwavelength emissions, showing comparatively lower responses in the blueand red wavelengths, while comparatively higher responses in the greenand yellow wavelengths. As depicted, the robot 10 encounters a non-greenarea while moving forward and then immediately backs up. As shown, therobot 10 may have encountered something red, but the signal of interestis the non-grass signal.

In additional implementations, a not-grass detector 330B includes aplurality of light emitters 332 having different green wavelengths whichare used for secondary color response tests, providing a lawn colorrange for further resolution. For example, the not-grass detector 330Bidentifies green but not the same green as cuttable lawn areas 20, 1020.A lawn color may be characterized over time as the mower robot 10 coversthe cuttable lawn area 20, 1020. Near IR, or UV black light LED's mayalso be used for the light emitters 332 in a similar manner.Polarization of the light emitted by the light emitters 332 (e.g. linearor circular) provides additional information.

In one example, gaff-like tape bearing unobtrusive detectableparticulate or stranded media (e.g. iron filings, retro reflectors, orthe like) is stuck onto a hard surface 1008, such as a driveway 1008A orsidewalk 1008B, and removed, leaving the detectable media adhered to thesurface 1008. The not-grass detector 330 detects the detectable media(e.g. light reflected off the detectable media).

In some implementations, the not-grass detector 330 also acts as a cliffdetector, since it points down and is angled to focus on an area ofinterest. The absence of any signal is detection of a cliff.

Referring to FIG. 8C, in some implementations, a not-grass detector 330Cincludes an ultrasound or acoustic emitter 333 and a microphone orultrasonic transducer 335 to record and measure acoustic reflections,e.g., echo attenuation, frequency shift or characteristics, to determinea grass presence grass. Hard surfaces 1008 (e.g. driveways 1008A,sidewalks 1008B, and roads 1008C) reflect sound better than grass 20,1020.

Referring to FIG. 8D, a grass sensor 330D includes a rolling idler wheel336 (e.g. driven wheel) acoustically monitored by a microphone orpiezoelectric pickup 335 for one or more characteristic frequencies,peaks, RMS amplitudes, and damping representative of non-cuttable areas1008 (e.g. driveways 1008A, sidewalks 1008B, roads 1008C, andflowers/garden 1008D). In one example, the wheel 336 is turned in placeto generate a rotational resistance characteristic of non-cuttable areas1008. In another example, the wheel 336 defines grooves 337 (e.g.longitudinally, laterally, diagonally, or sequentially some of each)that enhance acoustic and rolling resistance information. In anotherexample, the robot 10 includes a pH or chemical sensor bare areas ofdirt or pine needles.

Referring to FIG. 8E, the grass sensor 330, in some examples, includesan acoustic surface sensor 330E having a sensor housing 3310 definingemitter and receiver receptacles 3313 and 3314, respectively. An audiotransmitter 3311 (e.g. a piezo-electric element, or moving coil andmagnet assembly) is carried in the emitter receptacle 3313 and transmitsan audio emission 3315 downwardly. A receiver 3312 (e.g. apiezo-electric element, or moving coil and magnet assembly) is carriedin the receiver receptacle 3134 and is configured to receive a reflectedaudio emission 3316 off a ground surface 3340. A controller 3350monitors a received reflected audio emission 3316 and compares a maximumreceive energy with a threshold energy to classify the surface as hardor soft. The audio transmitter 3311 transmits multiple audio emissions3315, each having successively larger wavelengths increased by half afundamental frequency. In one example, the audio transmitter 3311transmits a first audio emission 3315 at about 6.5 kHz (wavelength ofabout 52 mm) and a second audio emission 3315 at about 8.67 kHz. Thestep in transmission frequency between the first and second audioemissions 3315 changes the acoustic energy by a half of a wavelength ofa fundamental frequency (e.g. by 26 mm). Small variations in a distancebetween the acoustic surface sensor 330E and a target surface 3340 maycause large variations in receive energy due primarily to constructiveand destructive interference.

In some examples, a relatively narrow band-pass amplifier 3362 limitsexternal acoustic interference for reflected audio signals 3316 receivedby the receiver 3312. A receive envelope detector 3364 receives aconditioned signal from the band-pass amplifier 3362. The receiveenvelope detector 3364 is in communication with an A/D converter 3366,which is in communication with the controller 3350.

Using an audio transmitter 3311 and receiver 3312 separate from eachother shortens a minimum sensing distance relative to a single unittransmitter—receiver. A single unit transmitter—receiver (e.g. inpulse-echo mode) generally has a wait period after a transmission forringing to attenuate before the unit 330E can listen for a reflectedtransmission 3316.

Referring to FIG. 8F, operation of the acoustic surface sensor 330Ecommences by step S100 of initializing a transmission frequency, stepS102 of initializing a frequency counter, and step S104 of zeroingvariables for a maximum peak signal received and maximum energyreceived. In step S106, a sound propagation timer is zeroed. In stepS108, the controller 3350 communicates with a transmit driver 3330,which communicates with the audio transmitter 3311 to generate audioemissions 3315. For each frequency step, the controller 3350, in stepS110, samples an amplitude of the receive envelope detector 3364 anddetermines a maximum reflected energy off the target surface 3340. Instep S112, if a peak amplitude of the receive envelope detector 3364 isnot greater than a maximum peak signal, the acoustic surface sensor 330Eproceeds to step S120, of decrementing the frequency counter. Otherwise,in step S114, the peak amplitude is stored as the peak amplitude of thecurrent wavelength; in step S116, a maximum energy received is stored asthe maximum energy received for the current wavelength; and in stepS118, a determined target distance is stored. In step S122, if thefrequency counter is zero, the acoustic surface sensor 330E incrementsthe frequency in step S124 and loops back to step S106. If the frequencycounter is not zero, the controller 3350, in step S126, compares amaximum receive energy with a threshold energy to classify the surfaceas hard or soft.

Referring to FIG. 8G, in some implementations, the receiver 3312 andoptionally the transmitter 3311 are mounted with an anti-vibrationmounting system 3370 in a manner that minimizes vibration transferencefrom the housing 3310. In the example shown, the receiver 3312 issecured with a high durometer rubber 3372 (e.g. Shore value of 70 A bythe ASTM D2240-00 testing standard) in a tube 3374. The tube 3374 issecured in the receiver receptacle 3314 with a low-durometer rubber 3376(e.g. Shore value of 20 A by the ASTM D2240-00 testing standard). Soundabsorbing foam 3378 is placed above the receiver 3312 in the tube 3374.An adhesive 3779 (e.g. epoxy) may be used to secure leads 3380 from thereceiver 3312 in the receiver receptacle 3314.

Referring to FIGS. 1 and 9, in some examples, the robot 10 includes aliquid detector 350 for detecting a liquid presence in its path. In oneexample, as shown in FIG. 1, the liquid detector 350 is positionedtoward the front of the body 100 to provide detection of a liquidquagmire before the drive system 400 contacts the potential obstacle.The liquid detector 350 aids the robot 10 in avoiding inadvertentlyfalling into a body of water 1004C (or losing traction therein). Theliquid detector 350, in some instances, includes two polarized lightemitters 352A and 352B, respectively, and a polarized light detector354. The polarized light emitters 352A and 352B, respectively, emitmutually cross-polarized beams of light angled downward. The polarizedlight detector 354 is polarized with regard to one of the two lightemitters 352A, 352B and positioned to detect whether a specularreflection has been removed from a generally quiescent surface of aliquid body 1004C (e.g. water).

In some examples, the liquid detector 350 includes a sonic sensor, likethe grass sensor 330 shown in FIG. 8C, that emits a sonic signal anddetects its echo. The liquid detector 350 discerns an echocharacteristic of water 1004C from an echo characteristic of grass 1020or an otherwise non-water surface. Microwave or radar echoes may be usedto discern the same characteristics. In other examples, the liquiddetector 350 includes a capacitive or magnetic sensor which detects ashift in capacitance or magnetic field when proximal to water 1004C.

Upon detecting a pond or other body of water 1004C with the liquiddetector 350, the robot 10 performs a behavior consistent with obstacleor cliff avoidance. For example, the robot 10 alters its heading awayfrom the detected body of water 1004C, backs up, or issues an alarm.

Referring to FIGS. 10-22, the robot 10 includes a cut edge detector 310to determine an edge between uncut and cut grass, 22 and 24respectively. In some implementations, cut edge sensing entails using aspan of sensors 312 to recognize different grass types, growth rates,and other lawn properties. The cut edge detector 310 generally includesa span of sensors 312 extending into the uncut grass 22 to provideself-calibration or normalization for another span of sensors 312intended to detect the edge between uncut and cut grass, 22 and 24respectively. The cut edge sensing techniques employed in robot 10 mayinclude combinations of rolling the cut grass 24 in front of the edgedetector 310, erecting the uncut grass 22 in front of the edge detector310, erecting the cut grass 22 behind the wheels 410, 420, 430, 440,behaviorally interpreting the cut edge 26 to robustly and smoothlyfollow the cut edge 26, and disposing more than one cut edge detector310 along the traveling length of the robotic mower 10.

Referring to FIG. 10, in some examples, the robot 10 includes an analogcut edge sensor 310A to detect the mowed regions 24 and un-mowed regions22 of a lawn 20 to ascertain the edge 26 defined therebetween. Oneexample an analog cut edge sensor 310A is provided in U.S. Pat. No.4,887,415, the entire contents of which are incorporated by referenceherein. The analog cut edge sensor 310A includes metallic strips 69, 70and 71 aligned laterally, orthogonal to a forward direction of travel ofthe robot 10, in which two of the metallic strips 69 and 70 projectdownward farther than the third metallic strip 71. As the robot 10proceeds forward while properly aligned to the cut edge 26, the twolarger metallic strips 69 and 70 contact the shorter grass of thepreviously mowed swath 23 in the cut area 22 while the shorter metallicstrip 71 contacts the taller grass of the uncut area 22. An electricalcurrent passes from the shorter metallic strip 71 to the larger metallicstrip 69 through moistened grass of the lawn 20. Generally, recently cutgrass of the mowed swath 23 will release moisture sufficient to permitelectrical conduction. When no current passage from metallic strip 71 tometallic strip 69 is detected, the robot 10 determines that it hasstrayed from alignment with the cut edge 26 and may alter its headinguntil the current is once again detected, for example.

Referring to FIGS. 11A-B, an alternative cut edge detector 310B isexemplified in U.S. Pat. No. 5,528,888 which is incorporated byreference herein in its entirety. The cut edge detector 310B may includea series of swing arms 80 that break electrical contact with a node 81when the cut edge detector 310B is in contact with sufficiently tallgrass of the uncut area 22. By positioning several swing arms 80 in arow in a comb-like fashion along a direction orthogonal to a forwarddirection of travel of the robot 10, the cut edge detector 310B candetermine that the cut edge 26 lies between first and second adjacentswing arms 80. The first swing arm 80 hits the tall uncut grass 22 andbreaks contact with the node 81, while the second swing arm 80positioned over the shorter grass of the mowed swath 23 maintainscontact with the node 81. As otherwise discussed herein, thisconfiguration may also use a calibration portion or sensor 320 separatefrom the cut edge detector 310B.

Yet another example of a cut edge detector 310 includes a polarizedlight emitter, reflector, and detector system, as illustrated anddisclosed in FIGS. 24-26 of U.S. Pat. No. 4,133,404, which isincorporated by reference herein in its entirety.

Other example cut edge detectors 310 for detecting the differencebetween the cut swath 23 and the uncut region 22 so as to determine theedge 26 therebetween include, but not limited to, an acoustic orpiezoelectric sensor, an optical sensor, and a mechanical or electricalsensor system.

When an analog cut edge sensor 310 is employed, a calibrator 320 mayalso be included to provide a reference for calibration and comparisonof the analog signal produced by the analog cut edge sensor 310. Ingeneral, the calibration sensor 320 provides a reference signal againstwhich the grass-trailing portion of the edge sensor 310 may benormalized or otherwise calibrated. In some examples, the calibrationsensor 320 will trail in lawns 20 having essentially the same breed,health, height, moisture content or dryness, weed or clover content,debris/mulch content and character, stiffness, cut history, sparseness,and dumpiness (and other variability) as the lawn 20 being followed foredge sensing. The calibrator 320 may include a sensor element identicalor similar to the cut edge sensor 310.

The calibrator 320 may be positioned underneath, in front of, or behindthe body 100, so long as the position of the calibrator 320 relative tothe body 100 is over the uncut grass area 22. The calibrator 320 (aswell as the analog cut edge sensor 310, for example) may be mounted soas to minimize the chance of a damaging collision with rocks, debris, orother obstacles. In some examples, the calibrator 320 includes a rigidrock shield or hood mounted in front of the calibrator 320 to shieldagainst collisions with debris larger than a clearance between thebottom of the rock shield and the ground 20. Preferably, the cut edgedetector 310 and the calibrator 320 are flexibly or pivotally mountedand/or floating at a certain height with respect to the ground 20 (e.g.by using a coupled wheel or skid to follow the ground 20 and/or movingtogether with a floating cutter 200 which may also employ a wheel orskid).

In many instances, the calibration sensor 320 is the same height as thecut edge detector 310. In some examples, as shown in FIGS. 1-3, thecalibrator 320 is positioned on the body 100 in a location exposed tothe tall grass of the uncut area 22. Accordingly, when the calibrator320 contacts the uncut area 22, it provides a reference signalcharacteristic of uncut grass 22. The robot 10 compares the signalprovided from the cut edge detector 310 to the signal from thecalibrator 320. In some instances, the cut edge detector 310 includes anarray of sensors 312 and generates multiple signals or one signal withmultiple portions corresponding to each sensor 312 or different regionsof the cut edge detector 310. A signal or portion of the signalcorresponding to a region of the cut edge detector 310 in contact withthe uncut area 22 may substantially resemble a signal from thecalibrator 320. Conversely, a signal or portion of the signalcorresponding to a region of the cut edge detector 310 exposed to apreviously mowed swath 23 will substantially differ from a signal fromthe calibrator 320. The heading of the robot 10 as it mows along the cutedge 26 is enhanced by continuously calibrating the cut edge detector310 with the calibrator 320.

One example calibrator 320 includes one or more optical sensors. Theoptical calibrator 320A is a “break-beam” type sensor where a beam ofinfrared, visible, or other frequency of light emitted laterally towarda detector is interrupted with the presence of grass. Another exampleincludes a capacitive or static sensor as the calibrator 320. In oneinstance, an electrical capacitance arising between an electricallycharged conductor connected to the robot 10 and the grass of the uncutarea 22 is detected. In another instance, static electricity generatedby friction between the robot 10 and the tall grass of the uncut area 22is detected. Other examples of calibrators 320 include sonar (which maybe similar to the optical break-beam detector, substituting sound wavesfor light), acoustic (detecting noise indicative of tall grass as therobot 10 passes over it), displacement-to-magnetic, or any other sensorcapable of indicating the difference between taller uncut grass 22 andshorter mowed grass 24.

In some implementations, where the optical calibrator 320A includesmultiple optical sensors, the emitters and receivers of the opticalsensors may include fiber optics, light pipes, multi-way reflectors andthe like. In one example, a plurality of optical emitters may bereplaced with a single emitter and an optical element that directs theemission in more than one direction. In another example, a plurality ofoptical detectors may be replaced with a single detector and an opticalelement that collects the emission from more than one direction.Conductive, capacitive, or electromagnetically resonant sensors may becombined, averaged, or weighted by connecting them to a conductiveelement or antenna. These sensors may use one sensor to collect signalsfrom more than one location or direction. Multiple contact sensorsresponsive to vibration, such as microphones and piezoelectric elements,may be replaced by one or more members that conduct vibration to thesensor, and these also may use only one sensor to collect signals frommore than one location or direction.

In some examples, high or distinctive frequencies of signals providedfrom the cut edge detector 310 and the calibrator 320 (e.g. optical,camera, vibration, acoustic, or other signal discussed herein) areprocessed or subject to transforms suitable for frequency domainanalysis to characterize meaningful frequencies and to removemeaningless frequencies. For example, acoustic signals may be processedto remove or ignore both cyclic components and low frequency noise frommotors, wheels, bearings, and/or cutters and identify “white noise” inthe frequency range expected for blades of grass striking the detectorsduring forward movement of the robot 10. Low-pixel camera, optical, andother signals may be processed similarly.

In some implementations, the type of sensor employed in the cut edgedetector 310 and calibrator 330 are the same, in order to simplify thecomparison of the calibration signal to the cut edge detector signal.However, these sensors 310, 320 may be different and signal comparisonis facilitated by normalization or conditioning of one or both of thesignals.

Following an edge smoothly is somewhat analogous to following a wallsmoothly. Once an appropriately conditioned signal is obtained, therobot 10 may perform signal interpretation and analysis and obstaclefollowing algorithms, as disclosed in U.S. patent application Ser. No.11/166,986, by Casey et al., filed Jun. 24, 2005 and titled OBSTACLEFOLLOWING SENSOR SCHEME FOR A MOBILE ROBOT, as well as U.S. Pat. No.6,594,844; U.S. patent application Ser. Nos. 10/453,202; 09/768,773; andU.S. Provisional Application Nos. 60/582,992 and 60/177,703, all ofwhich are incorporated by reference herein in their entireties. In thiscase, the “obstacle” or wall is the cut edge 26. In addition to the edgefollowing algorithm, in some examples, the robot 10 includes algorithmsfor determining or estimating the end of a row/swath 23 and turning toestablish a new row while depending on the cut edge 26.

FIG. 12 shows a rear schematic view of an example of a robot 10including wheels 410, 420, a body 103, a cut edge detector 310, and acalibrator sensor array 320. The cut edge detector 310 and thecalibrator sensor array 320 each include a plurality or span of sensors,312 and 322 respectively, projecting into the lawn 20. The sensors 312of the cut edge detector 310 project into the cut edge path 26. Inseveral instances, some of the sensors 312, 322 may detect grass andsome or all are positioned with respect to a cutting height (e.g. heightof the cutter 200 and cutting blades) so that they do not detect cutgrass 24. The signals from multiple sensors 312 and 322 may be combined,averaged, filtered to provide one or more simple grass-no grass signalsin digital form, or encoded (n bits of left-to-right grass/no-grassdistribution).

Example arrangements of the plurality or span of sensors, 312, 322include lateral spans, front-to-back sets, and diagonal spans. Differentarrangements provide different advantages in detecting grass andcollecting averaged or cumulative data.

Referring to FIG. 13, in some implementations, the robot 10 includes acut edge detector 310C having light sensors 380 mounted on struts 313extending from a sensor mount 311. The light sensor 380 includes an IRor visible light emitter 382 coupled with a receiver 384. In someexample, the emitter 382 and receiver 384 are angled toward an area ofinterest/distance of interest. The emitter 382 may be stepped up inpower until reflected illumination is detected by the receiver 384. Timeof flight and/or phase measurements may be used to detect grass 20 inthe area of interest. An active acoustic emitter and receiver may beused in a similar way, in addition detection echoes or the attenuationof echoes over time.

FIG. 14 shows an infrared (IR) sensor 390 including a light emittingdiode (LED) 392 and phototransistor 394 pointed at and mounted oppositeeach other. Each is shielded from stray light by short black tubes 396(e.g. heat-shrink tubing of about ⅛″ i.d.). Light reaching thephototransistor 394 from the LED 392 is measured by synchronousdetection, using cliff-sensor technology as discussed herein. Thissystem can detect single or multiple grass blades with a verticalresolution of about ¼ inches. LED power levels, distance between IRemitter 392 and detector 394, and diameter and length of the opticaltubes 396 are all parameters that can be varied.

Referring to FIG. 15A, in some implementations, the robot 10 includes acut edge detector 310D having emissive sensors 390 mounted on struts 313extending from a sensor mount 311. The emissive sensors 390 include anIR or visible light emitter 392 and receiver 394 positioned and alignedwith each other such that an emission passes through an area or distanceof interest. The receiver 394 may be configured to detect a partial orfull obstruction. Time of flight or phase measurements may be used todetect grass in an area of interest. An active acoustic emitter andreceiver may be used in a similar way.

Referring to FIG. 15B, in some implementations, the robot 10 includes acut edge detector 310D having one or more front-to-back emitter-receiversensor pairs 390. In some instances, several emitter-receiver sensorpairs 390 arranged with a detection axis in a forward direction detectmore grass than if arranged transverse to the forward direction. Eachemitter-receiver sensor pair 390 may provide one bit or several bits.Multiple front-to-back sensor pairs 390 form a lateral array spanningthe cut edge 26 to provide a signal for following the cut edge 26.

In some implementations, each sensor 312, 322 or sensor array 310, 320is arranged to rotate back or fold up and return when the mower robot 10encounters obstructions or obstacles at the height of the cutter 200 orabove. In some instances, the mower robot 10 stops the cutter 200 fromcutting when an obstruction has caused the sensor array 310, 320 to flipor rotate upward.

Referring to FIG. 16A, in some implementations, the robot 10 includes acut edge detector 310D having a sensor housing 3910 defining a cavity3930 and a cavity opening 3932 configured to allow grass 22 entry whileinhibiting direct sunlight 3990 into the cavity 3930. The cavity 3930may be colored a light absorbing color (e.g. black) or made of a lightabsorbing material. Grass 20 is inherently springy and may pop-up afterdeflection. The sensor housing 3910 is mounted to deflect uncut grass22, while passing over uncut grass 24, as the robot 10 maneuvers acrossthe lawn 20. The sensor housing 3910 allows the deflected uncut grass 22to self-straighten upward through the cavity opening 3932 and into thecavity 3930. In some examples, the sensor housing 3910 is mounted to thebody 100 at height relative to a ground surface that minimizes entranceof cut grass 24 the cavity 3930. An emitter-receiver sensor pair 3900,in communication with the controller 3350, is carried by the housing3910 and includes an IR or visible light emitter 3920 and receiver 3940(e.g. photon detector). The emitter 3920 is positioned inside the cavity3930 and configured to emit an emission 3922A across the cavity opening3932. The receiver 3940 is positioned below the emitter 3920 andconfigured to receive a grass reflected emission 3922B, while notreceiving any direct sunlight 3990. The receiver 3940 has a definedfield of view that intersects a field of emission across the cavityopening 3932. In preferred examples, the emitter-receiver sensor pair3900 is arranged so that grass 20 below a certain height substantiallydoes not reflect emissions 3922 back to the receiver 3940.

Referring to FIGS. 16B-C, in some implementations, the sensor housing3910 is configured to carry an array of emitter-receiver sensor pairs3900 (also referred to as grass height sensors) equally spaced apart andin communication with the controller 3350. The sensor housing 3910 maybe linear along a longitudinal axis 3911 defined by the horsing 3910 orcurved and located on a forward portion of the body 100. In someexamples, dividers 3914 separate each emitter-receiver sensor pair 3900.The array of grass height sensors 3900 may span the entire width or onlya portion of the width of the body 100. In some examples, a portion ofthe array of grass height sensors 3900 is used for the calibrator 320.For example, one half of the array of grass height sensors 3900 providesedge detection, while the other half provides calibration. As the robot10 travels forward, grass height estimates are acquired by the grassheight sensors 3900 based on signal strength of the receiver 3940 fromreflected emissions 3922B. One example of measuring signal strength isturning the emitter 3920 off, measuring a first signal strength of thereceiver 3940, turning emitter 3920 on, measuring a second signalstrength of the receiver 3940, and obtaining a difference between thefirst and second signal strengths. The resulting difference in signalstrengths is used for the sensor measurement (grass height signal) andgenerally has lower signal-to noise ratios. A grass height signalobtained by each grass height sensor 3900 is compared by the controller3350 to a threshold value, above which grass is considered uncut andbelow which grass is considered cut, and stored as binary decisions in agrass height row vector 3905, as shown in FIG. 16C. Periodically, thecontroller 3350 compares the grass height row vector 3905 to previouslystored exemplar row vectors 3905B representative of ideal grass edgemeasurements at each sensor pair array position 3906 to determine alocation of the cut edge 26 along the sensor array. With N number ofgrass height sensors 3900 in the array, there are (N−1) possible edgepositions each having a stored exemplar row vector 3905B, plus “nograss” and “all grass” stored exemplar row vectors 3905B. The controller3350 selects the exemplar row vector 3905B (and corresponding grass edgearray position) having the minimum number of differences (element byelement) with the compared grass height row vector 3905 to determine thelocation of the cut edge 26 along the sensor array 310D and therefore acut edge position 26 under the body 100. The number of differences withthe selected exemplar row vector 3905B is called the “grass edgeclarity”. The cut edge position and grass edge clarity may be used toinfluence the drive system 400 to create a grass edge followingbehavior.

The following example grass height vector Vx was acquired from an arrayof eight sensors 3900. Vx=[0 1 0 0 1 1 1 0]

Table 1 below provides exemplar grass height vectors 3905B andrespective edge positions for an eight sensor array.

TABLE 1 Exemplar Grass Height Vectors Edge position [0 0 0 0 0 0 0 0]0—no grass [0 0 0 0 0 0 0 1] 1 [0 0 0 0 0 0 1 1] 2 [0 0 0 0 0 1 1 1] 3[0 0 0 0 1 1 1 1] 4 [0 0 0 1 1 1 1 1] 5 [0 0 1 1 1 1 1 1] 6 [0 1 1 1 1 11 1] 7 [1 1 1 1 1 1 1 1] 8—all grass

Table 2 below provides the number of differences between the examplegrass height vector Vx and each exemplar grass height vector 3905B.

TABLE 2 Exemplar Grass Height Vectors Differences with V_(x) (EdgeClarity) [0 0 0 0 0 0 0 0] 4 [0 0 0 0 0 0 0 1] 5 [0 0 0 0 0 0 1 1] 4 [00 0 0 0 1 1 1] 3 [0 0 0 0 1 1 1 1] 2 [0 0 0 1 1 1 1 1] 3 [0 0 1 1 1 1 11] 4 [0 1 1 1 1 1 1 1] 3 [1 1 1 1 1 1 1 1] 4

In the example above, the controller 3350 selects the exemplar rowvector [0 0 0 0 1 1 1 1] (and corresponding grass edge array position of4) as having the minimum number of differences (element by element) withthe compared grass height row vector Vx. The fourth grass edge arrayposition from a total of eight sensors 3390 is approximately the centerof the detector 310D.

Referring to FIG. 16D, in some implementations, the use of a onedimensional vector 3905 for estimating a cut edge position and grassedge clarity is extended to a two dimensional model 3907 (e.g. atwo-dimensional array) having a sliding window of M row vectors 3905representing successive binary readings of the N grass height sensors3900. The number of row vectors 3905, M, included in the two dimensionalarray 3907 depends on the frequency of measurements made over adistance, X, traveled by the robot 10 in a period of time, T. In oneexample, the sensors 3900 measure grass height at a frequency of 512 Hz.A summation of differences between exemplar row vectors 3905B andmeasured grass height row vectors 3905 is performed in the same mannerdescribed above, except on a row by row basis. The results of thecompared rows may be averaged. In some examples, column data issummarized into a single summary row vector, where a row element 3906 isdesignated as “uncut” (e.g. by a corresponding 0 or 1) if any of theelements in that column contained an “uncut” designation.

Referring to FIG. 16E, in some implementations, a peak grass heightsignal 3962 is determined for each sensor 3900 or a combination ofsensors 3900 by combining grass height results from adjacent sensors3900 (e.g. of 1-2 adjacent sensors 3900 on one or both sides of thesensor 3900). The controller 3350 compares the peak grass height signals3962 against stored threshold values, as described earlier, to determineif the grass is cut or uncut. In one example, the array of grass heightsensors 3900 is divided into pairs of adjacent sensors 3900 and a peakgrass height signal 3962 is determined for each pair of adjacent sensors3900. A grass height image 3960, as shown in FIG. 16E, is createddepicting the peak grass height signals of the grass height sensors 3900or combinations of sensors 3900. The horizontal axis of the imagerepresents the array of N grass height sensors 3900 and the verticalaxis represents the number of measurements made within window of travel,X, by the robot within a period of time, T. Depending on the method ofobtaining the peak grass height signals 3962, each pixel 3964 mayrepresent a peak (or avenge) value for a combination of sensors 3900 oronly one sensor 3900 over a period of time. The pixel 3964 may have acolor and/or intensity proportional to grass height signal strength. Thecontroller 3350 compares an array of pixels (e.g. 4 pixels wide by 1pixel high or 16 pixels wide by 16 pixels high) with one or more storedreference patterns (of the same array size) of different possible edgeconfigurations. Different criteria may be employed in matching referencepatterns with sample arrays to determine the location of the cut edge26. With pattern matching, the controller 3350 can determine theorientation of the cut edge 26 with respect to the robot 10. Forexample, while searching for a cut edge 26 to follow, the robot 10 candetermine an approach angle when encountering a cut edge 26 based on theorientation of the orientation of the cut edge 26 with respect to therobot 10. In the example shown in FIG. 16E, the darker pixels 3964Arepresent weaker the peak grass height signals 3962 characteristic ofcut grass 24 and the lighter pixels 3964B represent stronger the peakgrass height signals 3962 characteristic of uncut grass 22. The boundarybetween the lighter and darker pixels 3962 provides the estimatedlocation of the cut edge 26. In this particular example, the robot 10,while executing an edge following behavior, mannered left and right tofollow the cut edge 26, hence the vertical zig-zag appearance. As anenergy saving technique, the robot 10 may turn off the cutters 200 tosave power while detecting all cut grass 24 and then turn the cutters200 on again once uncut grass 22 is detected.

The drive system 400 maneuvers the robot 10 while keeping the grass edge26 centered in the array of grass height sensors 3900 of the cut edgedetector 310D. In one implementation, the drive system 400, configuredas a differential drive and at least one passive front caster, in oneexample, uses the determined grass edge 26 to steer the robot 10 byselecting a turn radius. The further left the determined grass edge 26is of the center of the array of grass height sensors 3900, the shorterleft turning radius selected by the drive system 400. The further rightthe determined grass edge 26 is of the center of the array of grassheight sensors 3900, the shorter the right turning radius selected bythe drive system 400. The turn radius is proportional to an error inedge placement (i.e. location of the cut edge 26 with respect to thecenter of the robot 10.) In another implementation, when the determinedgrass edge 26 is left or right of the center of the array of grassheight sensors 3900, the drive system 400 turns the robot 10 left orright, respectively, as sharply as possible while keeping both left andright drive wheels 410 and 420, respectively, moving forward. The drivesystem 400 drives the robot 10 straight when the determined grass edge26 is centered on the array of grass height sensors 3900.

Several robotic behaviors are employed to achieve mowing coverage of thelawn 20. In some implementations, the behaviors are executed serially(versus concurrently). The highest priority behavior is a perimeterfollowing behavior. While creating the perimeter following behavior, therobot 10 follows a perimeter through bump sensing or the use ofconfinement devices (e.g. boundary responders 600). This tends to createcut grass edges 26 around obstacles and property perimeters that canlater be followed using a cut edge following behavior. The next highestpriority behavior is cut edge following. The cut edge following behavioruses the grass edge position as estimated by the grass edge sensor array310D to control the heading of the robot 10. The grass edge followingbehavior creates a new cut edge 26 behind the robot 10 that closelymatches the contour of the edge 26 it was following. The next highestpriority behavior is a tall grass turn behavior, which is executed afterthe robot 10 detects all uncut grass as estimated by the grass sensorarray 310D for a predetermined amount of time, such as five seconds.Using only dead reckoning, the robot 10 performs a tight turn to bringthe grass edge sensor array 310D back into the grass edge 26 just cut bythe robot mower 10. The robot 10 may maintain a history of the cut edgesensing to allow approximations of the location of the last detected atedge 26. The robot 10 may also drive in a random direction or pattern(e.g. spiral) to find a cut edge 26. The tall grass turn behavior isdesigned to avoid fragmentation of the lawn 20 into many islands ofuncut grass 22 that need to be found through random traverses ratherthan through methodical cutting by following a grass edge 26.

Referring to FIG. 17, in some implementations, the robot 10 includes acut edge detector 310E having a flap 302 of sufficiently flexiblematerial to which the sensors 312, 322 are secured. The sensors 312, 322move together with the flap 302 when an obstruction is encountered. Thesensors 312, 322 are arranged to precede the cutting head 200 in adirection of mower robot 10 at a height at or near the cutting height.In some examples, the sensors 312, 322 include microphones (alone orattached to strips of material), piezoelectric transducers, conductors,capacitors, or excited transducers with damped or interferedwavelengths. Each detector or transducer 312, 322 is arranged such thata disturbance by contact with a blade or clump of grass is detectable(by movement, vibration, bending, conductivity, capacitance). Thedetectors 312, 322 may be isolated from the supporting continuous flap302 or able to detect disturbances of the flap 302 (which may provide anaveraged signal). In some cases, only a protruding tip of the detector312, 322 may be sensitive (e.g., for piezoelectric material excited bybending).

Referring to FIG. 18, in some implementations, the robot 10 includes acut edge detector 310F having multiple sensors 312 extending downwardfrom a sensor mount 311 and including a vibration (or signal) sensor 315mounted to a sensor probe 313 (i.e. signal or vibration conductors). Thesensors 312 are arranged such that a disturbance by contact with a bladeor clump of grass is detectable (by movement, vibration, bending,conductivity, capacitance). The flexibility and/or drape of the probes313 may be similar to string, chain, bristles, or stiff pins, and may beselected to dampen, attenuate or filter vibrations detrimental to thedetection of uncut grass 22. The length of the probe 313 serves totransmit the vibration or signal to the signal sensor 315, and in somecases, to attenuate, damp, or filter the signal or vibration. In oneexample, a piezoelectric strip sensor 312A includes a strip of thinpiezo film 315A deposited on a Mylar substrate 313A (or individualstrips mounted to individual struts 313). The sensor 312A is mounted toallow deflection by blades of grass, or deflection by a moving finger incontact with the blades of grass. The sensor 312A produces a voltageoutput when mechanically deflected that is proportional to the amountand rate-of-change of deflection. The sensor output may be subject tosignal filtering and amplification.

Alternatively, a lightweight detector member may be rotatably mounted toa potentiometer, hall sensor, mechanical switch, or optical encoder(reflective or transmissive photo-interrupter) that measures detectormember rotation from encountered grass in an amount proportional tograss density, height, thickness, etc.

Referring to FIG. 19, in some implementations, the robot 10 includes acut edge detector 310G having a vibration (or signal) sensor 315 mountedon a continuous contact flap 303. The flexibility of the flap 303 may besimilar to a thin plastic sheet, metal foil, or sheet metal, and may beselected to dampen, attenuate or filter vibrations detrimental to thedetection of uncut grass 22 as well as to average multiple signalsconducted by the flap 303. Examples of the vibration (or signal) sensor315 include a microphone, a piezoelectric transducer, a conductivesensor, a capacitive sensor, and an exciting transducer. Resonating orstanding waves geminated by the flap 303 may be dampened or subject tointerference with the exciting transducer separate from a detectiontransducer. The vibration (or signal) sensor 315 is configured to detectflap disturbances by movement, vibration, bending, conductivity,capacitance, etc. (e.g. from contact with a series of blades or clumpsof grass). The edge sensor configuration shown in FIG. 18 capturescontacts across the width of the flap 303.

Referring to FIG. 20, in some implementations, the robot 10 includes acut edge detector 310H and calibrator 320B carried by the body 103. Thecut edge detector 310H is a crenellated flap 303A with separate flapportions 304 providing either separation or flexibility to isolate,dampen, attenuate or filter vibrations or other conducted signalsdetrimental to the detection of uncut grass 22. The separate calibrationarray 320B trailing in the uncut grass 22 provides a signal fornormalizing or continuously calibrating a grass detection signalprovided by the cut edge detector 310H. In the example illustrated, thecalibrator 320B includes a first crenellated flap 303A and a secondrelatively longer crenellated flap 303B. The second relatively longercrenellated flap 303B detects a complete lack of grass (e.g., as asecondary or complementary grass sensor 330).

Multiple sensors 312, 322 may be placed into the grass 20 (e.g. withprobes 313 or flaps 303) at different heights, e.g., in crenellated,staircase, or other stepped fashion, to provide additional informationand resolution. In some instances, the sensors 312, 322 are actuatedupward and downward by a motor or linkage to measure obstruction,reflection, or conducted signal (including sound) at different heights.In some additional instances, the sensors 312, 322 (and all of or asubset of the associated struts, probes, sensors, or flaps) are actuatedupward and downward by a motor or linkage to follow a grass height asdetected or as predicted.

Referring to FIGS. 21-22, in some implementations, a rotating cut edgedetector 310I, rotating in a horizontal or vertical plane, replacesmultiple sensors 312, 322 and increases a signal frequency. Forconductive sensors, a rotating cut edge detector 310I, rotating in ahorizontal plane, may be used. The rotating cut edge detector 310Iincludes a rotating disk 316 configured with protrusions/spokes 317 orslots/depressions 318 which rotate with the disk 316 to increase thefrequency and intensity of contacts with the grass 20. The size of therotating disk 316 determines the averaged area for a signal, anddifferent disk sizes may be used in different locations on the robot 10.Alternatively, the same disk size may be used in situations in which thedisk size controls the resonant frequency, capacitance, or othersize-dependant property. In some examples, a disk height is adjustable(e.g. via a motor or links) according to grass height, orincreased/decreased periodically. The signal provided is characteristicof grass rubbing against, contacting, or striking the disk 316. Forexample, the signal may be characteristic of acoustics, vibrations, ormechanical resistance (to rotation) from the grass 20. The rotating cutedge detector 310I provides signal readings while the robot 10 isstationary as well.

The cut edge detector 310, in some implementations, resolves the cutedge 26 down to about plus or minus an inch horizontally, ½ inchpreferably, and resolves the cut edge 26 down to about plus or minus ½″height, ¼″ preferably. In some examples, the cut edge detector 310detects an edge 26 when approaching from a first direction between about30-90 degrees to a second direction normal to the cut edge 26. In otherexamples, the cut edge detector 310 detects the edge 26 when approachingfrom between about 0-30 degrees from a direction normal to the cut edge26.

In some implementations, the robot 10 includes a substantiallyhorizontally oriented forward sensing boundary sensor 340. In someinstances, a reflection type sensor as shown and described herein withreference to FIG. 13 is used. In other instances, the boundary sensor340 is a camera or passive reception sensor. In many cases, the cliffdetection sensor would be of analogous type. The boundary sensor 340detects, for example, flowers, bushes, and fragile flexible structuresnot detectable by a depressible bumper soon enough to prevent damage. Insome instances, the boundary sensor 340 is configured similarly to themulti-frequency color-based grass sensor 330 described earlier. Theboundary sensor 340 may be filtered, shuttered, partially covered, orthe signal therefrom conditioned, to emphasize vertical and diagonallines typical of plant stalks and trunks.

FIG. 23A is a schematic view of a lawn care robot system 5 including arobot 10 and boundary responders 600. Boundary responders 600 placed onor in the ground 20 constrain or influence a behavior of the robot 10.In some implementations, the autonomous robot 10 includes a boundaryresponder emitter-receiver unit 1500 including a signal emitter 1510which continuously or periodically emits a signal (e.g. aradio-frequency, electro-magnetic wave, or an acoustic signal) and asignal receiver 1520. In other implementations, the emitter 1510 is notnecessary with certain kinds of active or semi-active boundary responder600. Examples of boundary responders 600 include passive resonantboundary responders and powered active radio-frequency identification(RFID) boundary responders. Passive boundary responders echo or generatea responsive signal to a signal emitted from the robot 10 that isdetected by the signal receiver 1520. Passive resonant boundaryresponders are detected by measuring the energy transferred from theemitter 1510 operating at a resonant frequency. Each of the boundaryresponders 600 discussed may be structured to drape well, in the mannerof loose chain with a small bend radius (e.g., less than 2 inches,preferably less than 1 inch). In some examples, active boundaryresponders 600 are only powered when the robot 10 is within a certainrange.

When the robot 10 approaches and detects a boundary responder 600, therobot 10 initiates a responsive behavior such as altering its heading(e.g. bouncing back away from the boundary responder 600) or followingalong the boundary responder 600. The boundary responder 600, in someexamples, passively responds to a signal emitted by the signal emitter1510 of the robot 10 and does not require a connection to a centralpower source such as an AC power outlet or origin dock. In otherexamples, the boundary responder 600 is a powered perimeter wire 6012that responds to a signal emitted by the signal emitter 1510 of therobot 10. The powered perimeter wire 600 may be connected to a centralpower source such as an AC power outlet or origin dock. The poweredperimeter wire 6012 may also be provided on a spool and cut to lengthfor application. The powered perimeter wire 600 may also be provided inpre-cut length for application having connectors at each end of thepre-cut wire. In some implementations, passive and active boundaryresponders 600 are both detected by the same robot antenna 1520.

Referring to FIG. 23B, in some implementations, the signal emitter 1510is a circuit 1514 including an antennae loop 1512 configured as afigure-eight, which creates a null in the antennae loop 1512 to preventringing and minimizes transmitted signal coupling into the receiverantennae 1522 thereby allowing earlier detection of a received pulse inthe time domain. The signal receiver 1520 is a circuit 1524 including anantennae loop 1522 surrounding and coplanar with the antennae figureeight loop 1512 of the signal emitter 1510. The figure-eight antennaeloop 1512 coplanar with the receiver antennae loop 1522 provideincreased detection range for the same amount of transmitting power overconventional coplanar antennae loops. An emitter-receiver control unit1515 controls the signal emitter 1510 and receiver 1520 and communicateswith the drive system 400. The emitter-receiver control circuit 1515activates the signal emitter 1510 for a period of time. The signalemitter 1510 emits a radio frequency (RF) signal (e.g. at 13.56 MHz) topassive boundary responders 600 tuned to the transmitted frequency.Inductive and/or capacitive circuits 620 in the passive boundaryresponders 600 absorb the RF energy and re-radiate the energy back tothe signal receiver 1520 (e.g. at a frequency other than 13.56 MHz). There-radiate signal will persist for a period of time after the signalemitter 1510 has ceased emissions. The detected signal is processed bythe emitter-receiver control unit 1515 and communicates a boundaryresponder presence to the drive system 400. Depending on the type ofboundary responder 600, the drive system 400 may direct the robot 10away, over, or to follow the boundary responder 600.

Referring to FIG. 24, a boundary responder 600 includes a boundaryresponder body 610 having one or more inductive and/or capacitivecircuits 620 (herein termed “tank circuits”). The tank circuits 620 maybe formed, deposited, or printed on the boundary responder body 610. Forexample, the tank circuits 620 may be formed on the boundary responderbody 610 by photolithography, in a manner similar to silicon integratedcircuit manufacturing; printed onto the boundary responder body 610using ink jet or other depositional techniques; or manufacturedindividually and affixed to the boundary responder body 610. The tankcircuits 620 may include localized compact folded/concentric loops, orloops extending along the length of the cord or tape body 610A. Althoughthe boundary responder 600 is shown as a flat tape with printedcircuits, the circuits 620 may include longer concentric, spiraled orother antenna-like elements, and may be constructed in a tape-like formwound or rolled into a cord-like or wire-like form.

In some examples, the boundary responder 600 has a predictable resonancefrequency by having the boundary responder body 610 formed as acontinuous cord or web with discrete inductive/tank circuit elements 620of a known responsive frequency.

In general, tank circuits 620 are known and used in different arts. Forexample, low frequency versions are placed to facilitate the detectionof buried cables (e.g., 3M Electronic Segment System, U.S. Pat. Nos.4,767,237; 5,017,415), trapped miners (U.S. Pat. No. 4,163,977), orswallowed radioendosondes (e.g., the Heidelberg capsule), such as U.S.Pat. Nos. 6,300,737; 6,465,982; 6,586,908; 6,885,912; 6,850,024;6,615,108; WO 2003/065140, all of which are expressly incorporatedherein by reference in their entireties. When tank circuits 620 areexposed to a magnetic pulse or electromagnetic energy at a particularfrequency they will ring for a time at a frequency determined by thecapacitor and inductor. Each tank circuits 620 may be tuned to the samefrequency, in some examples, and for better discrimination tuned to twoor more different frequencies, in other examples. In someimplementations, the robot 10 pulses a transmitter 1510 and looks for aresponse from the tank circuits 620 of the boundary responders 600. Inother implementations, the robot 10 sweeps a transmitting frequency andlooks for a response at each particular frequency. Certain types ofreceiving coils for the signal receiver 1520 (a figure-8 coil, forexample) can detect a phase shift as an external tank circuit 620 passesa centerline of the coil, allowing the robot 10 to detect when itcrosses the boundary responder 600. In some examples, a receiving coilor antenna of the signal receiver 1520 and the tank circuits 620 of theboundary responders 600 are disposed in parallel planes.

In some implementations, the boundary responder 600 includes amorphousmetal, which may remain passive but emit a responsive signal when itreceives an electromagnetic signal. When the boundary responder 600composed of amorphous metal (either entirely or partially) receives anelectromagnetic signal, for example, the amorphous metal becomessaturated and emits a spectrum of electromagnetic signals, includingharmonic frequencies of the received incoming electromagnetic signal.Amorphous metal requires very little magnetic field to become saturated.When an amorphous metal is exposed to even weak RF energy the metal goesinto and out of magnetic saturation during each cycle. This provides anon-linearity in the metal's response to the radiation and results inthe production of harmonics to a fundamental frequency. This property isquite rare in normal environments. In some implementations, to detect aboundary responder 600, the robot 10 generates a signal (e.g. modulatedfrequency) to excite any nearby amorphous metal which will radiateharmonics of the transmitted frequency. The robot 10 detects theharmonics of the radiated frequency (using synchronous detection, forexample) to determine a locality with respect to the boundary responder600.

In some examples, the emitter 1510 of the robot 10 emits anelectromagnetic signal as it traverses a yard 20. Upon approaching aboundary responder 600, the boundary responder 600 receives theelectromagnetic signal from the robot 10 and emits a responsive signalincluding harmonics of the received electromagnetic signal. The signalreceiver 1520 of the robot 10 receives and analyzes the responsiveelectromagnetic signal using a circuit or algorithm. The robot 10 thenperforms a predetermined behavior (such as turning away from orfollowing the boundary responder 600, as appropriate).

A wire-like or tape-like boundary responder 600 including at least oneportion composed of amorphous metal does not need a tank circuit 620,thereby reducing manufacturing costs. When the boundary responders 600includes tank circuits 620 or is composed of amorphous metal (or both),the boundary responders 600 may be cut to length (at fixed or variableintervals), curved, bent, or otherwise manipulated for placement on orbeneath the yard 20. The boundary responders 600 may be supplied on aspool or reel, for example, and cut with scissors or garden shears intosegments of a particular length. The boundary responder 600 is affixedto the yard 20 by a number of methods, including, for example, placingit beneath thick grass; adhering it to the ground 20 using lime,concrete, epoxy, resin, or other adhesive (e.g., when traversingpavement such as a driveway or sidewalk), tacking it down with lawnnails or stakes, or burying it up to an effective depth of soil suchthat the boundary responder 600 can still detect and respond to incomingsignals.

The boundary responder 600 is severable or separable at and between thecircuits 620. Cutting boundary responders 600 made of amorphous metal orhaving many tank circuits 620 about its entire length does not destroythe ability of the boundary responder 600 to detect and respond toincoming signals. If one tank circuit is 620 is damaged during cutting,other tank circuits 620 located elsewhere along the boundary responderbody 610 will still function properly. When amorphous metal is cut, itselectromagnetic properties remain generally unchanged.

Referring to FIG. 25, a boundary responder 600A, in some examples,includes a circuit 620A having has one or more pairs of conductors (e.g.parallel wires) shorted together to form an inductor loop 622. Loadcircuits 624 may set a resonant frequency. In some implementations, thenarrow (e.g. ⅜″) wire loop 622 is constructed of parallel wires (e.g.300-ohm twin lead) with the ends shorted to create a loop inductorcapable of resonating at an appropriate wavelength (e.g., 100 MHz).Twin-lead is available in many forms, including antenna tape andinvisible twin lead (thin wires bonded to sticky tape). Although FIG. 24shows spaces between the circuits 620A (which may be marked with “cuthere” indicia of any kind), the boundary responder 600A, in someexamples, includes a boundary responder body 610 having continuous twinleads 622. Shorting shunts placed along the responder body 610 at fixedintervals (e.g. 1 to 6 feet) creates repeating circuits 620A. Theboundary responder 600A is severable or separable at the shunts betweencircuits 620A. The shunts may include loading inductors or capacitors tomake resonance less dependent on length.

Orientation of the detection antenna 1520 on the robot 10 may beappropriate to detect the circuits 620. The detection antenna 1520 maybe provided in a rotating loop or as three orthogonally arrangedimpedance balanced antennae components, which detects energy absorptionby the resonant circuit 620 at a known frequency. The configurationdepicted in FIG. 24 can power active RFID-type components.

Referring to FIG. 26, a boundary responder 600B, in some examples,includes spiral or multi-loop conductors 622 with optionally attachedloading elements (capacitor, inductor) 624. In cases where longercircuit loops 620 are used, e.g. 1-6 foot long inductive loops, theboundary responders 600 may be severed at marked places 626 (e.g.perforations) between adjacent circuit loops 620. In each case, theloading elements 624 are optional.

FIG. 27 shows a boundary responder 600C including a boundary responderbody 610 formed of multiple laminae 630. Each lamina 630 includesprinted, deposited, or etched loading elements 624 (capacitor, inductor)and/or loop inductors 622, or parts thereof. Some of the structures 622,624 may be completed by lamination of the entire responder body 610(e.g. parts of the loading elements and/or loops being distributed amongdifferent laminae). The lamina 630 may be single sheets of Mylar with adeposited shaped layer or metal foil etched to a desired shape.

FIGS. 28 and 37 depict a boundary responder 600D including a circuit620D arranged within a responder body 610D formed as a spike or tack. Insome examples, the responder body spike 610D includes a responder top612 visible above the ground 20. In some examples, the responder top 612is passively excitable, e.g., fluorescing and detectable by thenot-grass detector 330. The responder top 612 is a flag in some exampleswith loading elements 624 placed in a flagpole. In some examples, theboundary responder 600D is connected to an extended loop inductor 622 orextended antenna, with or without loading elements 624 in the responderbody spike 610D or flagpoles. The boundary responder 600D may beconnected to one another to form a stand. If loading elements 24 are inthe responder body spikes 610D, the resonance may be dominated by theloading elements 24, but an extending antenna 622 can distribute thelength of the circuit responsive to resonance between periodicallyplaced boundary responders 600D. In some examples, the tank circuit 620of the boundary responders 600 are disposed in a head portion of theresponder body 610D (e.g. to position the tank circuit 620 in a planeparallel to the signal receiver 1520 of the robot 10).

Referring to FIG. 29, in non-passive examples, a boundary responder 600Eincludes RFID emitters 625 in place of loading elements 624 and emittinga signal detectable by the signal receiver 1520 of the robot 10 and aloop 622E. The RFID tag 525 receives a signal transmitted by the signalemitter 1510 of the robot 10 and replies by broadcasting storedinformation. In some examples, the boundary responder 600E includes apower source (e.g. battery) to extend a range of the boundary responder600E (e.g. the robot 10 could detect the boundary 600E at a greaterdistance).

In some implementations, the boundary responder 600 includes one or moreacoustic devices which chirp when remotely excited to establish aboundary. In other implementations, the boundary responder 600 emitsand/or receives visible-spectrum signals (color codes or other encodedmessage passing, for example) via retro-reflectors or optical targets.Optical targets are distinguishable from other objects in a visual fieldof the robot 10. The optical targets may be printed with a“self-similar” retro-reflective pattern illuminable with modulatedillumination. The optical targets may identify endpoints of the boundaryresponder 600.

In one example, a boundary responder 600F includes a magneticallychargeable loop 622F. A moving (e.g. rotating) magnet carried by therobot 10 transfers energy. For example, a magnet is placed on a movingpart of the cutter 200 (e.g. a spinning blade, or oscillating shears).The boundary responder 600F is installed in or on the ground 20 with theloop 622 orientated to derive sufficient flux through the loop 622. Thematerial of the rotating or reciprocating support for the magnet ormagnets should not short out the lines of flux (e.g., plastic ornon-conductors). In some examples, the magnetically chargeable loop 622Fis used to wakeup a battery powered continuous loop 622D.

In another variation, a boundary responder 600G includes a plastic cablebody 610G with fluorescence embedded therein or painted thereon,activatable with a UV radiating source (e.g. LED) on the robot 10 andseverable to any length. The fluorescence boundary responder 600G, insome examples, is masked or embedded to encode (e.g. long, short, long)a responder kind. In still another variation, a boundary responder 600Hincludes a quarter or half-wave antenna or inductor-loaded antenna,detectable by resonance, re-radiation, or energy absorption in a similarfashion to the tank circuits 620 previously discussed herein. Again,different frequencies may be detected. If the boundary responder 600H iscut to length, a first pass by the robot 10 establishes a frequency tobe expected on that particular lawn 20. In still another variation, aboundary responder 600I includes a flat responder body 610I definingrumble strips vibrationally or acoustically detected and preferablyarranged with distinctive periodicity to generate distinct frequenciesfor detection.

FIG. 30 provides a schematic view of a property 1001 with a propertyinterior 1001A having a house 1002 surrounded by cuttable areas 1020(e.g. a grassy lawn 20), grass-cutting obstacles 1004 (e.g. trees 1004A,bushes 1004B, and water 1004C, and immovable objects 1004D), boundaries1006 (e.g. fences 1006A and property lines 1006B), and non-cuttableareas 1008 (e.g. driveways 1008A, sidewalks 1008B, and roads 1008C, andflowers/garden 1008D).

Referring to FIG. 31, an example mower system installation for aproperty 1001 includes arranging boundary responders 600 along thelength of a neighboring property line 1006B. There is no particular needto arrange segments along the sidewalks 1008B or street 100BC, as thesewill be detected as described herein. The flower bed 1008D, which isboth fragile and difficult to detect, is also protected with a boundaryresponder 600. The remainder of the obstacles 1004, 1006 in the property1001 are detected by a sensor suite of the robot 10 as described herein.In this case, most of the lawn 1020 is contiguous with a few areasbounded by pavement 1008B. The mower robot 10 can be lead to the boundedareas or provided with a behavior that follows boundary responders 600to the bounded areas. For example, a behavior may direct the robot 10 tofollow the boundary responders 600 across pavement or mulch 1008 withthe cutter 200 turned off, but not across a drop or cliff. A cliffsensor suitable for detecting such cliffs or drops is disclosed in U.S.Pat. No. 6,594,844 and incorporated by reference herein in its entirety.

Referring to FIG. 32, in some examples, multiple types of boundaryresponders 600 exist. Boundary responders 600 including resonantcircuits 620 (whether using lumped or distributed inductance andcapacitance) may have different resonant frequencies to convey boundarytype information. In one example, a passive boundary responder 6010signals the robot 10 to maneuver over it and whether mowing shouldstart, continue, or halt. The passive boundary responder 6010 may alsotrigger the robot 10 to perform other actions upon detection. Forexample, a follow type boundary responder 6010A signals the robot 10 tofollow the responder 6010A for its entire length (e.g., to cross adriveway or navigate a long dirt or pavement path between zones). Inanother example, an enter type boundary responder 6010B signals therobot 10 to enter an area normally off-limits (e.g., to navigate along asidewalk to get from front to rear yards or to continue cutting across apath of separated flagstones). In yet another example, upon detecting ado not enter type boundary responder 6010C, the robot 10 initiates abehavior to alter its heading to bounce back away from the boundaryresponder 6010C.

In some implementations, the powered perimeter wire 6012 and the passiveboundary responders 6010A-C both operate at the same frequency (e.g. at13.56 MHz). The powered perimeter wire 6012 has a duty cycle,alternating between powered and un-powered, to not overshadow signalsfrom passive boundary responders 6010A-C located on a property 1001circumscribed by the powered perimeter wire 6012. When the poweredperimeter wire 6012 is quiet, the signal receiver 1520 can detectpassive boundary responders 6010A-C. The duty cycle is set to allow therobot 10 to quickly alternate monitoring of active responder 6012 andpassive responder 6010A-C confinement while maneuvering across the lawn1020.

After installation of the boundary responders 600, the robot 10 maytraverse the property 1001 without any cutters 200 activated to checkthe placement of boundary responders 600. In some instances, the robot10 is configured to operate only when within a certain range of theboundary responders 600 or when the boundary responders 600 are active(e.g. for safety purposes). For example, the robot 10 is configured todetect a current direction in boundary responders 600 powered withalternating current to determine whether it is inside or outside of aboundary perimeter. Other techniques of preventing robot escapes includeusing GPS to determine a robot location, determining a distance from abeacon, and using virtual walls including beacons that emit an emission(e.g. infrared light or radio frequency) detectable by the robot 10. Insome examples, the robot 10 employs proximity detection to protectagainst moving into people or pets. A radio frequency identification tag(RFID) recognizable by the robot 10 may be placed on people or pets toprevent their collision with the robot 10.

Robot navigation components may be divided into five sub-categories:follow cut grass edge (i.e. find the boundary between the cut and uncutgrass); stay on the grass (i.e. passive grass/not-grass detection); staywithin the arbitrary boundaries (i.e. don't cut the neighbor's lawn);don't stray too far (e.g. backup/secondary system); and end near aspecified location. The backup system, for example, may be a radio-baseddetector restricting the robot 10 from traveling too far from a homebase (which would be optionally integrated with a battery chargingdevice). Some implementations include using a GPS circuit, determining asignal strength of the responder 600, or resolving a time of flight froma local encoded beacon. As a security and/or safety measure, the robot10, in some examples, may not operate other than within a restrictedcoordinate set, or absent an appropriate signal. To minimize error andsignal loss from weather, canopy or obstacles, the robot 10 may betrained with the signal characteristics of the property 1001 (e.g. thefirst full cycle of mowing the lawn would collect baseline signal datafor determining minimum and maximum thresholds of the property 1001).This provision may also be overridden by the user with appropriateauthorization. A beacon or GPS signal may aid the robot 10 in returningto an end location specified by the user, or an additional short ormid-range radio or visible beacon provided for homing purposes.

U.S. Pat. No. 6,690,134 by Jones et al., entitled Method and System forRobot Localization and Confinement, the entire disclosure of which isherein incorporated by reference it its entirety, discloses methods forconfining and localizing an indoor robot using directed IR beams andmulti-directional sensors; and U.S. Provisional Patent Application No.60/741,442, “Robot Networking, Theming, and Communication System,” filedDec. 2, 2005, which is herein incorporated by reference in its entirety,discloses additional methods for chamber-to-chamber localization,confinement, and navigation using different frequencies and ranges of IRbeams and multi-directional sensors. These can be used as, incombination with, or instead of, the boundary responders 600 discussedherein. Although the use of IR beams and detectors is less effectiveoutdoors, various implementations may use higher wavelengths of IRemission and detection (e.g., 900 nm+). The IR emission and detectionmay be baffled, channeled, and filtered to remove sunlight and/orsunlight spectral components. The IR emission and detection may also bemodulated to permit AC coupling on receivers to reject daylight andother steady light sources. Narrow beam (5 degrees or less) microwave(e.g., in conventional radar gun/detector frequencies) emitters anddetectors can be used instead of, or in addition to, directed IR beams(complementary false positive rejection) with the same interpretingsoftware and behaviors.

Referring to FIG. 33, in some examples, the mower robot 10 includes oneor more tilt sensors 710 (e.g. accelerometers) monitoring a robot tiltto avoid mowing or maneuvering above a maximum robot tilt angle. Thetilt sensor 710 may also provide terrain data that aids robotmaneuvering and behaviors. For example, when the tilt sensor detects arobot tilt, the robot 10 compares a measured robot inclination withknown values to determine whether it is maneuvering over a threshold,tree roots, humps, hillocks, small hills, or other surface phenomenathat may be treated as obstacles, but not easily detectable by bumpersor proximity sensors.

In some examples, the mower robot 10 includes a rain sensor, such thatit returns to a home base when rain is detected.

The robot 10 includes at least one stasis detector 442, in someexamples, such as an idle wheel sensor (e.g., optical, magnetic, limitswitch encoder on non-driven wheels) or a drive wheel torque/currentsensor for detecting a stuck condition. The cut edge sensor 310 or edgecalibration sensor 320 is used as a stasis sensor in some cases, or as abackup sensor for a wheel torque/current sensor type stasis sensor. Anycamera, including optical mouse-type or other low-pixel cameras, evenwhen used for other purposes (e.g., grass/no grass), can be used as astasis sensor when no movement is detected. In some cases, a motor loadof the cutter 200 is monitored for a stasis or stuck condition. Anycombination of these can be interpreted as a stuck condition when thecircumstances giving rise to that response are appropriate (e.g., nograss detected+no cutting load=stuck, unless front wheel is rotating andmotor load is normal).

In some implementations, the robot 10 includes additional obstacledetectors such as bump, infrared, optical, sonic, andhorizontal-scanning sensors for detecting collision hazards (i.e.chain-link fences) within a path of the robot 10. In one example, ahorizontally oriented sonic sensor is capable of detecting a flower potor tree trunk prior to a collision, enabling the robot 10 to alter itsheading to avoid the obstacle.

In some examples, the robot 10 includes a clipping collector 720, suchas a sack or barrel for collecting grass clippings or yard debris. Theclipping collector 720 includes a capacity sensor 722, in oneimplementation. Examples of the capacity sensor 722 include an acousticsensor that analyzes an acoustic spectral response of a substantiallyrigid clipping barrel and a break-beam optical sensor. The break-beamoptical sensor has an emitter projecting a beam of light across theclipping collector to a receiver. When the beam of light is not detectedby the receiver, the robot 10 determines that the clipping collector 720is full and performs an appropriate behavior such as ceasing mowing, ordumping the contents of the clipping collector 720 at a designatedlocation, for example.

In some examples, the robot 10 communicates wirelessly with a remotemonitor, also discussed interchangeably herein as a wireless remote ableto communicate with transceiver 55 on the robot. The remote monitor is asmall console or indicator, in some instances, not significantly largerthan 3 cubic inches. The remote monitor may be affixed to a refrigeratordoor or other metal object using a magnet. The remote monitor signals toan operator that the robot 10 needs assistance when the robot 10 becomesstuck, damaged, unsafe for operation, or unable to empty the clippingcollector, for example. The remote monitor may include a kill switch toterminate operation of the robot 10; and/or may transmit a dead-mansignal without which the robot 10 will not operate. In one example, therobot 10 sends a radio-frequency signal via an unlicensed frequency(e.g. 900 MHz or 2.4 GHz) to the remote monitor. The wireless signal mayencode information via frequency or amplitude modulation, for example,and/or via any appropriate communications standard such as Bluetooth,ZigBee, WiFi, IEEE 802.11a, b, g, n, wireless USB (UWB), or aproprietary protocol such as discussed in U.S. Provisional PatentApplication No. 60/741,442, “Robot Networking, Theming, andCommunication System.”

A base station acts as a relay or intermediary, in some instances,between the robot 10 and the remote monitor. In some examples, the basestation includes a charging system and communicates with a wired orwireless home network. The remote monitor sounds an audible alarm(particularly if the signal issued by the robot indicated that adangerous condition or accident had occurred) and/or flashing light orother signal, for example, to bring a robot distress condition to theattention of an operator. The remote monitor may communicate datatransmitted by the robot 10 on a display (e.g. LCD) or via a voicesynthesizer. Examples of transmitted data include area of lawn mowed,remaining power level, and warning alarms.

A base station and an autonomous robot configured for autonomouslydocking and recharging is specifically described in U.S. patentapplication Ser. No. 10/762,219, by Cohen, et al., filed on Jan. 21,2004, entitled Autonomous Robot Auto-Docking and Energy ManagementSystems and Methods, the entire disclosure of which is hereinincorporated by reference it its entirety. User input commands,functions, and components used for scheduling a mowing cycle directly onthe robot 10 or via the base station and/or any boundary responders 600are specifically described in U.S. patent application Ser. No.11/166,891, by Dubrovsky et al., filed on Jun. 24, 2005, entitled RemoteControl Scheduler and Method for Autonomous Robotic Device, the entiredisclosure of which is herein incorporated by reference it its entirety.

In some implementations, the robot 10 mows a swath 23 having a generallyspiral path, combined with boundary following, edge following, andrandom movement. Spiral spot cleaning essentially equivalent to spiralmowing as well as wall following essentially equivalent to obstacleand/or boundary responder following are specifically described in U.S.Pat. No. 6,809,490, by Jones et al., entitled, Method and System forMulti-Mode Coverage for an Autonomous Robot, the entire disclosure ofwhich is herein incorporated by reference it its entirety.

The robot 10 may have a single dominant following side 101, 102, or letone side 101, 102 dominate depending on whether a boundary 600, 1004,1006, 1008 or cut edge 26 is to be followed. Boundary responders 600 maybe followed differently from physical boundaries, e.g., on the robotedge, the cut edge, or the robot center. When the cutting head 200extends fully across one side 101, 102 of the robot body 100 but not theother, either side 101, 102 of the robot 10 may still be a dominantand/or boundary following side. The robot 10 follows obstacles 1004,1006, 1008 on the side 101, 102 having greatest cutter extension to cutas close to an edge as possible, yet may still follow cut edges 26 onthe other side 101, 102.

Alternatively, the robot 10 may follow both cut edges 26 and boundaries600, 1004, 1006, 1008 on the same side 101, 102 with an asymmetricalblade arrangement 200. An asymmetrical cutter 200 leaves an uncut spot,e.g., where the cutting head 200 is offset to the right and the robot 10spirals to the left, the bottom portion of the robot 10 with no cuttinghead coverage creates a small uncut circle in the center of the spiral.This can be addressed by adding to the spiral a center pass based ondead reckoning, or by following the spiral with one or two center passfigure-eights based on dead reckoning, or by reversing the direction ofthe spiral.

FIG. 34 provides a schematic view of an alternative non-random coveragepattern 3000 by the robot 10. The pattern 3000 is suitable for robots 10having offset and non-offset cutting heads 200. To make the pattern3000, the robot 10 follows a succession of offset overlapping loops3005, such as those traversed by Zamboni® ice resurfacing machines. Ageneral wheel path 3010 is shown in dotted lines and a general coveragepath 3020 is shown in solid lines. The overlap is sufficient to coverany uncut spots caused by the offset cutting head 200 or offsetdifferential drive system 400. The pattern 3000, in one example,includes as a series of overlapping rounded-corned rectangles achievedby right-angle differentially steered turns. In other examples, thepattern 3000 includes smooth ovals. A distance across each loop 3005 ofthe pattern 3000 can be any size. Larger loops 3005 incorporating manysubstantially straight lines provide greater cutting efficiency thansmaller loops 3005. However, drift error may accumulate with large loops3005, disrupting the pattern 3000. If the loops 3005 are too small, toomuch time is spent turning. A cutting quality during turning may not beas satisfactory as while cruising straight. A balance of cuttingperformance, speed, and loop size may be established for each yard 20.In one example, the loop 3005 is sized to completely cover a center ofthe loop 3005 on a third to sixth parallel pass (parallel whether theloop 3005 is irregular, circular, oval, square, or rectangular) andoverlaps by no more than half of a cutting width on each pass. Examplepatterns 3000 include loops 3005 overlapping by about 120%-200% of adistance 107 from a wheel center to an edge of the cutting head 200,loops 3005 offset by a cutting width 108 minus about 120%-200% ofdistance 107, loops 3005 overlapping by about ⅕-⅓ of the cutting headwidth 108, and loops 3005 offset by about ⅘-⅔ of the cutting head width108, having loops 3005 less than three to four times as wide as the yard20. In many instances, the loops 3005 are substantially symmetrical. Thepattern 3000 is adjusted to leave no gaps in the cut area 22 for a robot10 cutting to a following or dominant side edge 101, 102, or having acutter 200 that does not extend to the edge on either side 101, 102.

With any cutting path, it is not critical that the rows are straight,but more important that the robot follows its previous pass/swath 23.The reference swath 23 may be parallel to a curved or stepped obstacle.Following previous swaths 23 improves efficiency, as compared to randombouncing (reducing time on the working surface from 5× deterministic to1.5-3 times deterministic), and improves a user's perception of therobot's effectiveness and aesthetics of the lawn 20.

A method of mowing a yard includes placing an autonomous mower robot 10in a yard 20 and allowing the robot 10 to mow a reference row/swath 23of arbitrary or boundary-constrained length. The robot 10 proceeds tofollow a cut edge 26 of the reference row/swath 23. At the end of thereference row 23, the robot 10 turns and row follows for each successiverow 23, mowing a pattern 3000 as described above. The pattern 3000 hassuccessive offset overlapping loops 3005 that spiral and increase insize with each iterative loop 3005. The robot 10 continues mowing byfollowing the cut edge 26 of a preceding row 23 until an arbitrary areahas been cut or the pattern 3000 is interrupted by an obstacle 1004 orboundary 1006. The robot 10 then moves to a new uncut area 24 of lawn 20(randomly or using collected boundary history), mows a new reference row23, and repeats the mowing process until the lawn 20 is estimated to becomplete. The robot 10 uses a reference heading from a navigationalsystem to establish each reference row 23, the edge of which is followedto mow substantially parallel rows.

In addition to or in lieu of the cut edge sensor 310, in some example,the robot 10 includes one or more auxiliary navigational systems toenhance alignment and navigation of the robot 10. For example, the robot10 may include a global positioning satellite (GPS) receiver, a radiosignal time-of-flight sensor, an inertial guidance system including oneor more accelerometers or gyroscopes, or an optical landmark sensor. Anysingle positional system may suffer drift or continuously decreasingprecision during operation. Multiple positional systems enhancenavigational precision.

In one example, the robot 10 includes an electronic compass that returnsa heading accurate to about +/−6 degrees. In another example, the robot10 includes an odometer. In yet another example, the robot 10 includes aglobal positioning satellite (GPS) receiver, which provides a headingwithin a few degrees accuracy after traveling tens of meters in astraight line. By integrating the input from two or more heading systemsthe heading precision can be improved (for example, in accordance withany of the techniques set forth in U.S. patent application “Mobile RobotAutonomous Navigational and Obstacle-Avoidance System,” 60/754,635,filed Dec. 30, 2005, inventor Brian YAMAUCHI, the contents of which areincorporated herein by reference in their entirety). For instance, aftermowing a 100 meter swath 23, the robot 10 turns approximately 180degrees to start a new swath 23 and obtains a first heading vector fromthe GPS receiver. The GPS may render a degree of error of about plus orminus 6 degrees. The robot 10 obtains a second heading vector from anelectronic compass and compares the two heading vectors to determine anaveraged heading to follow.

If, for example, it is desired to approximate rows/swaths 23, the robot10 may obtain assistance from the heading. Rows/swaths 23 may be madeparallel by edge following or without edge following by a headingvector. Alternatively, the rows/swaths 23 may be slightly open andzig-zagged, e.g., opening by a degree amount larger than the headingerror every turn. The rows/swaths 23 may alternate parallel rows withclosed-angle rows, e.g., crossing back to redo a likely cut area 22 byeither more than the heading error or less than the row width everyturn. Each row/swath 23 is arranged to successively advance the mowedarea 22.

In one example, a hybrid compass/odometry localization technique is usedto determine a robot position. The compass is used to determine a robotorientation and odometry is used to determine a distance translatedbetween updates. The robot position is determined using the followingequations:Δ_(t)=√{square root over ((x _(t) −x _(t-1))²+(y _(t) −y_(t-1))²)}{square root over ((x _(t) −x _(t-1))²+(y _(t) −y _(t-1))²)}x _(t)′=Δ_(t) cos θ_(t)y _(t)′=Δ_(t) sin θ_(t)

where (xt, yt) is the odometry position at time t, θt is the compassheading at time t, Δt is the distance traversed between time t−1 andtime t, and (x′t, y′t) is the hybrid compass/odometry position estimatefor time t.

Odometry tends to accumulate error. Over a single traverse of the lawn20, odometry may accumulate over 90 degrees of orientation error, forexample. In contrast, a compass in conjunction with odometry enables therobot 10 to determine the robot position within a few degrees. Thehybrid compass/odometry localization method may determine a robotposition accurately to within a few meters after a circuit of the lawn20. The inclusion of one to three axes of accelerometer data increasesaccuracy as well. Any combination of odometry, compass, GPS, or inertialguidance may be processed by a Kalman filter if sufficient computationcapacity is available.

In examples using GPS, inertial or odometric guidance, landmarkrecognition and/or other dead reckoning or navigational sensors, therobot 10 can determine whether it has crossed a boundary 1006, 1008 intoa road, or onto a neighbor's property, for example, and take appropriatecorrective action (such as shutting down or navigating back to a homepoint or recognized landmark).

The robot 10 may align its initial row or each set of rows using apreferred heading. From row 23 to row 23, the robot 10 may use correctedheading data to avoid drift and maintain an appearance of successiverows. The robot 10 may use the corrected heading data to locate newareas to mow as well.

Referring to FIGS. 35A-D, as discussed above, the robot system 5 may usea combination of active boundary wire 6012 and passive guard barriers6010. The robot system may be provided with splice and/or terminatorconnectors 5910 for moving, rerouting, or repairing the active boundary6012. A typical rearrangement is shown in FIG. 35A, where a user haselected not to mow a driveway 1008A but instead reroutes the activeboundary 6012 using two splice connectors 5910. The splice connectors5910 may butt-splice or side-by-side splice a single or dual conductor,and are preferably tool-less snap-closed connectors that include a bladethat penetrates insulation and connects the wires 6012. The spliceconnectors 5910 may also be terminators, e.g., terminating adual-conductor length to become a loop. The splice connectors 5910 maybe used to connect wire 6012 provided as discrete lengths. An examplesplice connectors 5910 is shown in FIG. 35B. As shown in FIG. 35A, theentire active perimeter 6012 may be a combination of wire lengths andsplice connectors 5910 (not excluding other devices which may be placedalong the perimeter). In some cases, the splice connectors 5910 may beprovided with test circuits useful for checking the position of a breakin the boundary (e.g., if each splice connector includes a socket,conductor loops can be tested by connecting adjacent splice connectorsusing a test line with a detector (e.g., lamp), or by plugging in a testlamp at subsequent splice connectors).

FIGS. 35A and 35C, depicts robot-activated power stations 5912 placedalong the active perimeter 6012. The robot-activated power stations 5912may be battery and/or solar powered, which may in some cases permitisolated lengths to be used or a main extension 5920 from household ACto the powered perimeter boundary 6012 to be avoided. Some powerstations 5912 may include an emitter, receiver, or antenna, as well ascontrol. The robot 10, in this case, is provided with an emitter 1510that “excites” nearby power stations 5912. For example, the robot 10 maybe provided with an RF or IR emitter 1510 of limited range that onlyactivates (“wakes up”) a power station 5912 when the robot 10 is in acertain range. The excitation range may be longer than the distancebetween any two to four power stations 5912. After a power station 5912is activated, it may hand-shake with the robot 10 over the receiverchannel using its own emitter or over another channel for communication(e.g., line-of-sight such as collimated or omnidirectional visible lightor IR) to ensure that a neighbor's power stations, for example, are notactivated. Implementations that activate a limited portion anywherealong an entire perimeter 6012 (e.g., a sector or sub-portion of theentire boundary including two to four power stations) only when therobot 10 approaches the perimeter 6012, allow the boundary 6012 to bebattery powered and/or use smaller batteries. The power stations 5912may be placed along, and bridge, single conductor or dual conductorperimeters 6012. In the case of dual conductors, any two power stations5912 or power station 5912 and terminator may close a circuit formed bythe dual conductors.

FIG. 35 shows an anchor 5930. An anchor 5930 may be a beacon including aprimary non-line of sight emitter of limited signal strength and mayinclude a secondary line of sight or directional emitter as well. Whenthe robot 10 travels outside the signal strength limit of the anchor5930, it may deactivate or may seek the anchor using the secondaryemitter. A virtual anchor may be provided using terrestrial navigationsignals, e.g., GPS. A robot 10 provided with a global positioning (GPS)receiver may be locked to a position approximately within the center ofthe yard to be cared for or mowed. Although commercial GPS typically hasinsufficient resolution to provide a useful location within most yardsand is not reliable under canopy or other natural barriers. GPS canprovide sufficient resolution to determine that the robot 10 is nolonger close to an anchor point 5930. A controller 452 on the robot 10may deactivate the robot 10 when it is sufficiently far (e.g., 100 feet)from its anchor point 5930; and may also activate an anti-theft claxon,radio beacon, lockout, or other countermeasure when the robot 10 is veryfar (e.g., greater than 200 yards) from its anchor point 5930.

FIGS. 36-38 depicts a typical use of passive “spike” type guard barriers600D. As shown in FIG. 36, the no-go boundary type passive spikes 6010Cmay be arranged to surround an area that would not be detected by hardsurface, boundary, bump, or other detections. The spikes 600D are placedat from one half to two robot working widths from one another, dependingon the antenna 1520 and emitter 1510 configuration of the robot 10. Thespikes 600D may be used in conjunction with the splice connector5910-type boundary or power station 5912 type boundary of FIG. 35. Asshown in FIG. 37, each spike 600D may include an RFID or tank circuitdisposed on a horizontal thumbtack-type head. The head 612 prevents thespike 600D from being pushed too far (more than 3-5 inches for a spikeof corresponding length) into the ground and burying the circuit 620 tobe detected. The perpendicular orientation of the spike-head circuit 620permits arranging the antenna or circuit 620 in the best orientation(e.g., parallel) to be excited and/or detected by an antenna 1510 on therobot 10. The head 612 may be provided with hooks or holes 612A formedtherein for using a line to check the distance between spikes.Optionally, each spike or some spikes may be provided with a flag 612B(e.g., “corner” spikes with a different resonant frequency or encoding,and used in corners, may be the only ones provided with small flags).

Spikes 600D may be easier to install if they are provided with aninstallation tool 5950. The tool 5950 may be a “spiking tool”approximately 36 to 48 inches in height (i.e., the approximate height orlower of a typical user's hip) and may be provided with a handle 5952 atthe top and a stirrup 5954 at the bottom. In use, a spike 600D may beplaced in the tool 5950 (either manually in a slot or loaded from thetop of the tool 5950 to fall into a receiving mechanism at the bottom).Then the tool 5950 is arranged to insert the spike 600D in the earth.The stirrup 5954 permits the user to use his or her weight to force thespike 600D into the ground. A measuring line 5956 may hang from the tool5950, and the measuring line 5956 may be hooked or fixed to alast-placed adjacent spike 5950 to set a distance from spike to spike.The tool 5950 may also be provided with a clamp or levering mechanism tomore easily close the splice connectors previously mentioned. The shaftextending from the handle 5952 to the stirrup 5954 may include atelescoping, folding, or other compacting mechanism to permit the tool5950 to stow in a smaller size. In this case, the clamp or leveringmechanism may be arranged for use with the tool 5950 in the smallersize.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. For example, the robot maybe used without a network. The network may be used without a robot. Adifferent mobility platform may be provided for the robot. No one (ormore) element or feature described is implicitly, explicitly, orinherently critical or necessary to the operation of the robot or lawncare system, except as explicitly described herein. Although severalsensor arrangements have been described as detecting grass along alateral line substantially perpendicular to the direction of forwardmovement, the sensor orientation itself may be front to back ordiagonal. Although reference has been made to lawn-mowing and/orshrub-trimming robots, it is nonetheless understood that any of thefeatures set forth also apply to any lawn care autonomous robot.Accordingly, other implementations are within the scope of the followingclaims.

What is claimed is:
 1. A robot lawnmower comprising: a body; a drivesystem carried by the body and configured to maneuver the robot across alawn; a grass cutter carried by the body; at least one obstacle sensorcarried by the body, the at least one obstacle sensor configured todetect when the body encounters a surface phenomenon that may be treatedas an obstacle; and a kill switch in a manual handle configured to beattached to the body and in communication with the drive system, thekill switch configured to turn off the cutter when the kill switch isnot manually depressed; wherein the drive system is configured tooperate in an autonomous mode when the manual handle is not attached tothe body and redirect the robot away from detected obstacles, andwherein the drive system is configured to operate in a manual mode whenthe kill switch is manually depressed.
 2. The robot lawnmower of claim1, wherein the drive system is configured to have a default kill switchoff condition when the detachable handle is attached to the body and adefault kill switch on condition when the detachable handle is detachedfrom the body.
 3. The robot lawnmower of claim 1, wherein the manualhandle is configured in the form of a conventional push mower handle. 4.The robot lawnmower of claim 1, comprising a user interface configuredto notify a user while in manual mode when obstacle sensor detects anobstacle.
 5. The robot lawnmower of claim 1, where in the body isconfigured to receive and stow the detachable manual handle.
 6. Therobot lawnmower of claim 1, wherein the drive system is configured todirect the robot at a faster speed during manual mode than in autonomousmode.
 7. The robot lawnmower of claim 1, wherein the obstacle sensorcomprises: a tilt sensor carried by the body, the tilt sensor configuredto monitor a robot tilt to provide terrain data to determine whether thebody is maneuvering over surface phenomena that may be treated asobstacles, a wheel drop sensor carried by the body, the wheel dropsensor configured to sense when at least a portion of the drive systementers an extended position indicative of loss of wheel contact with thelawn surface, or a water content sensor configured to sense watercontent indicative of a non-grass surface below the body and detectsurface obstacles indicated as water.
 8. The robot lawnmower of claim 1,wherein the drive system comprises right and left sets of forward andrear drive wheels, each set of drive wheels being disposed on acorresponding side of the body and differentially driven with respect toeach other.